There are many second acts in American technological lives -- and often third, fourth and fifth acts. They happen all the time: A price cut or a bug-fix update can redeem a previously woeful product while a lurking bug or compatibility glitch might sink a once-praiseworthy release.

This leads to a peculiar occupational hazard for those of us who write technology reviews, which can become as obsolete as the products they assess. So I've taken to devoting one column each year to update the last year's worth of work. Think of it as a version 1.1 bug-fix update for all those old columns -- without having to reboot to reap the benefits.

My glowing review of Apple's new iMac G5 desktop last September shows why such a revision is necessary. When I wrote that piece, I had no way of knowing that some of these slick, all-in-one computers, within months, would begin to overheat and exhibit wiring problems. These issues drew increasingly frequent discussions on Mac-troubleshooting Web sites, but Apple stayed silent on them until mid-August, when it said it would double the one-year warranty on many iMac G5s.

Fortunately, these troubles seem to have been addressed in the update to the iMac line that arrived in May. The revision also doubled the memory to 512 megabytes, increased processor speeds and made WiFi and Bluetooth wireless standard.

A similar alteration of Apple's $500 Mac mini arrived in July. Here, the doubling of memory alleviated one of my major quibbles with this attractive little machine.

My single most positive review of the past year was the rave I wrote about the Firefox Web browser in November. But I've since noticed that it's easy to miss the update alerts, leaving many Web surfers with an older, less secure version that could be targeted by writers of computer viruses.

The Palm Treo 650 phone/handheld organizer that I tried out in December as a Sprint PCS-only product is now also sold by Cingular and Verizon. It's unsettling to see how widely these carriers' rates for Web and data use vary: Sprint charges $15 for unlimited access, Cingular's data plans start at $20 for just 5 megabytes of use, and Verizon's begin at $30 for 10 megabytes.

Also unsettling: these carriers aren't all rolling out Palm's software updates at the same pace. Cingular has been the fastest, with Sprint trailing and Verizon moving the slowest.

In both my Treo review and my subsequent evaluation of Palm's Tungsten E2 and LifeDrive handheld, I should have also taken a swat at Palm's aging, increasingly shaky desktop software. As I've been reminded in day-to-day use of a Treo 650 since July, too many hot-sync hiccups can only be cured by restarting the Palm, the computer or both.

The biggest handheldcomputing debut of 2005, Sony's PlayStation Portable, is doing better than I'd expected. There is a growing number of movies available in Sony's proprietary UMD format and people apparently are buying them. (I'm still mystified as to why, seeing how UMD movies can cost as much as DVDs but only play on the PSP.)

In August, Sony released a free software upgrade that lets the PSP browse the Web. This works fairly well in practice, but pages take their time to appear -- and typing out their addresses using the PSP's weird on-screen keyboard is the only form of text entry that's more annoying than using a cell phone's numeric keypad.

The biggest software release of 2005, meanwhile, came from Apple -- Mac OS X 10.4 Tiger. This April release has since seen two major bug-fix updates and a set of smaller security patches, which suggests that waiting to upgrade (as I counseled at the time) was the right idea.

In daily use, Tiger has been extraordinarily stable. But I've found I'm making relatively little use of its two most-hyped features, Dashboard "widgets" and Spotlight searching.

Dashboard's weakness has been the notable delay it takes to invoke this collection of small reference and utility programs when it hasn't been used in a while. I've waited almost 20 seconds to see my Dashboard widgets pop into view and respond to my input -- although on subsequent occasions, Dashboard's ready in a second or two.

Spotlight's ability to find things on your computer by reading the contents of your files remains near-miraculous, but this power can become an obstacle, as well. If you only need to find a file by its name and don't want to risk having hundreds of other files show up in response to a Spotlight search, you can limit your query to file names only -- but that takes too many clicks.

Furthermore, to help Spotlight search e-mail, Apple revised its Mail program to store messages as separate files instead of grouping them in mailbox files. So in Tiger, e-mail takes up more space -- to the point that it now takes a higher-capacity recordable DVD, not just a CD, to back up my old messages. That's an unnecessary nuisance. Similar file-search programs for Windows have no problem dealing with conventional mailboxes.

I tried a batch of these Windows desktop-search downloads in March and found that Google Desktop outranked the others. Since then, Google and its rivals Copernic, MSN and Yahoo have all released noteworthy updates.

Copernic's new software can now find messages stored by non-Microsoft mail programs, while Yahoo's provides a far cleaner interface. MSN's updated Search Toolbar, meanwhile, also offers a makeover for Internet Explorer. But its new tabbed-browsing option looks and acts like a crudely bolted-on addition, to the point where just switching from tab to tab causes the entire browser window to flash distractingly.

Google's update is by far the most ambitious; look for a review of Google Desktop 2.0 in this space next week.

Music-download sales continued to grow throughout the year -- Apple's iTunes store, the leading retailer in this category, has now sold more than 500 million songs. But new music-subscription services have arrived and they allow their users to download all the songs they want for a monthly fee, play them on computers and transfer them to some newer music players.

Among them, Yahoo's Music Unlimited made headlines with its $5 monthly fee (though it requires paying for a year of service) when it arrived in May. At the time, Yahoo called this an "introductory price," but it's now sticking with that rate. So how long will competitors Napster To Go and Rhapsody Unlimited keep charging three times as much for the same basic rental service?

In a year with so many worthy, free software downloads, the most interesting came in July, when Google released Google Earth, a three-dimensional mapping program. Despite my initial sense that this might be nothing more than a nifty-looking gimmick, I've found that I use it all the time to do things like plan out-of-town weekends and plot new running routes. In the process, however, I've also seen some addresses misplaced by anywhere from one house to half a block. Blame for this must go to the databases used by Google Earth, as the same errors crop up in the Web mapping sites run by MapQuest and Yahoo.

Lastly, I've rarely been more pleased to have been wrong than in my guesses about prices for high-definition TVs. In January, I ventured that $2,500 might buy a 37-inch flat-panel set by this summer. Prices have plunged far faster than that. One name-brand 42-inch plasma screen TV on Amazon has dropped from $2,700 to below $2,400 -- since Monday.

I can only hope the technology industry will offer more pleasant surprises like that over the next year, even if some of my columns wind up looking silly afterward.

Living with technology, or trying to? E-mail Rob Pegoraro at rob@twp.com.