I'll skip past other answers to the bottom to answer this (it's late and I'd rather answer than read for a while first).
If you can rehab your desktop and use it for the basic heavy-lifting (image editing, Adobe-type software, big storage, copying DVDs or CDs, etc.) then you don't need to get a whole big computer.
They make these "web devices" now (netbooks, primarily) that are small, don't do everything a big computer would do without having a USB plug attachment added, but they're great for email, browsing, and light-weight web stuff. They're portable, and they're wired to look for Internet access. AND--you can hook it to your big desktop monitor, your regular keyboard, and your printer (if it has a USB cable) to the small device.
You can move big files to the larger computer via thumb drive or you can network them.
NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER NEVER consider buying anything larger than a blank CD or a paper clip at Best Buy. Their service sucks and they sell those extended warranties but offer miserable support. I'd sooner buy a device online from Amazon or pick it up at Office Depot. I like Fry's, if I'm walking in, and for online, you can't beat NewEgg.com. Just check with the manufacturer of the device first because they have so many variable options, like OS, number of ports, type of software pre-loaded, etc.