A friend of mine was asking for advice on what to look for in a new PC as he's looking to buy, I did a quick no-fuss guide, I thought it might be useful for other people so I've cleaned it up a bit and here it is:
Operating System - Stick with Windows XP, home or pro edition will be fine
CPU - Either Intel or AMD, go for a P4 or an Athlon, the Celeron and
Duron Sempron are low-budget versions but won't last as long
RAM - Nothing below 256Mb, 512 ideally, the more the better. RAM is cheap and you can always add more later.
Hard Disk Drive (HDD) - The bigger the better. Depending on what you're doing I doubt you'll fill a 40Gb disk, but size is on the increase all the time and so finding something as small as a 40 will be hard. HDDs are pretty cheap so don't be wowed by big storage figures (big is 200+Gb, anything else is ordinary).
USB ports will allow the connection of most peripherals these days and USB hubs can expand the number of ports you have (up to something like 256, so no worries there). Ideally, look for the option of USB ports on the front as well as the back.
Firewire (aka IEEE 1394) ports are useful, especially for video cameras and external storage. Think of them as like USB ports.
A DVD-ROM drive is a must, a DVD writer (DVD-R/DVD-RW) is nice but not essential unles you want to create DVDs or backup huge amounts of data. DVD drives that have CD writing (CD-RW) capabilities are about the same as standard DVD-ROM drives, useful to have the option to burn CDs.
Make sure you get a reasonable AGP graphics card (128 Mb of onboard memory ideally) and don't rely on any built in to the motherboard (they're slow, weak and steal memory from your RAM).
An on-board sound card is okay, better to have a separate card, especially as they're usually pretty cheap, but this optional unless you want stereo-quality sound.
As for software, personally I'd recommend staying away from Microsoft except for the OS, download free copies of Firefox (web browser) and Thunderbird (email), they're more secure. Also recommended are anti-virus and, if you're online, a firewall (don't trust the MS default, it's wimpy), both of which you should be able to download for free. Also try and get a free copy of a spyware detector (something like AdAware). Also make sure you switch auto-updates on on XP so you get the latest patches for the OS at all times.