If it's any help, I bought a Compaq machine just over a year ago - it was in a post-Xmas sale in my local computer store. It has an Athlon processor (2.17Ghz), 512 MB of DDR ram, a 120 GB HD and a DVD writer/+RW re-writer. Apart from a couple of niggles it works fine. Best of all though, it came with excellent documentation which actually makes sense!
The HD is great - I've got loads of MP3s, digital photos etc. on it and have barely made a dent.
The other great feature is (as someone mentioned above) 2 USB ports, firewire and line in/line out jack ports (or whatever they're called) on the front - what an innovation!! The latter feature means (among other things) that it is easy to plug your stereo amp into the machine and digitise all your LPs.
I suspect that computer nerds would tend to turn their noses up at a machine from a company as mainstream as HP/Compaq but I have never regretted my choice.