Q: I'm considering upgrades to a used laptop. Can I put in a faster processor? Add RAM? Put in 802.11n wireless? Replace the hard drive with an SSD?
A: Most desktops have allowed relatively easy processor upgrades, but that's not the case with laptops.
Random-access memory upgrades, however, are both feasible on most laptops and advisable. You just need to find your computer's memory slots, buy the right kind for it - look that up at comparison sites like dealram.com - and click it into place.
(You may need to remove one memory module to make room for a new one; make sure its replacement has enough capacity to make up for that.)
I wouldn't bother with a wireless upgrade unless a laptop is stuck on the very oldest version of WiFi, 802.11b. Most non-antique machines include 802.11g, which is more than fast enough and will still experience better range when connected to a wireless router running the newer 802.11n standard.
I would also save a drive swap for later. A solid-state-drive can shave some ounces off the laptop's weight, speed its bootup time, extend its battery life and end the risk of a hard drive's mechanism crashing. But flash memory costs a lot more than hard-drive memory, even after steady declines. Wait on that purchase, and you'll have better odds of not losing storage space in the bargain.
Q: I wanted to uninstall a program, but its installer started instead.
A: This can confuse beginners in Windows, where a program's installer often doubles as its uninstaller. Let the installer begin, then select "Remove" or "Uninstall" from its main menu and you should be fine.