Go to Dell.com
You can look at all different price ranges.
They are good for first systems that you want to work and not have to wonder about all the time.
Dell also extensively tests their products to work with all the options they offer, They have great support, and it is easy to know how to upgrade your system because it has an ID tag on it. You can go to their website and enter your ID tag and they will only present upgrades that will work in your system. Also, Windows comes installed as does a few other programs.
The company I work for buys almost exclusively Dells because of all this.
Go to www.bensbargains.net and select 'Computers' under the catagorys on the left. Search for Dell Deals, here is one they are offering today:
Rebate:
Dimension 5150 3.06GHz 512MB 80GB 19" $506 at Dell Business
Click Here
Discuss (8) : History : Posted 7:52 AM PDT 09/26/06 by Ben
Enter E-Value code AFFT-S50942a to find this Dimension 5150 Desktop (3.06GHz Core Solo) for $429. Add the 19 inch Ultrasharp 1907FP LCD, 16x DVD-ROM, and 3 Yr On-site Warranty (last page of config) for a total of $678 - $172 rebate = $506 with free shipping.
# Pentium 3.06GHz Core Solo, 512MB DDR2, 80GB SATA, 16x DVD-ROM, Intel GMA 950
# 10/100 Ethernet, 19" 1907FP Flat Panel, XP Home, 3-Yr Warranty
A really nice computer and 19" flat panel monitor for $500
good luck