QCan I install software on a USB memory

key?

AIt all depends on what you want to install on one of these thumb-size, flash-memory devices.

A few Windows programs are so simple they don't require running an installer when you add them to your computer -- you simply copy a program file to the folder of your choice. They should always work on a USB key. (This should also be the case with Mac OS X programs, which usually come as self-contained, no-installer-needed files.)

Most Windows software must be planted on a computer with the help of a separate installer program that copies over secondary files. Should those extra files go in a system directory -- something you can't tell in advance -- they'll tie the program to that one PC. But if an installer keeps a program and its supporting cast in one folder, the program should function on a USB key (or other removable media).

Even in that case, you'll have to redo any custom settings for that application each time you plug its USB key into a new machine. An exception: Versions of some software, such as the Firefox Web browser, have been tweaked to store their settings and data on the same drive as the program.

We've copied about a gigabyte of songs to our PC in iTunes, but now we're thinking of buying a non-iPod player. Can we change those songs from AAC to MP3 format?

Yes. Open iTunes, go to its Edit menu, select Preferences, click the "Importing" tab and change the "Import Using" choice from AAC (the default choice) to MP3. Select the songs you want to convert, then run the Advanced menu's "Convert Selection to MP3" command.

That will give you an MP3 copy of each song, although you may lose some sound quality in the process. You'll also need to use another music-management program, since the Windows version of iTunes will transfer song files only from a computer to an iPod.

-- Rob Pegoraro

Rob Pegoraro attempts to untangle computing conundrums and errant electronics each week. Send questions to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or rob@twp.com.