This blog post is a quick explanation of the hardware I'm using (laptop/desktop specs).
I currently have a "linxtop" (laptop with Linux Ubuntu/Backtrack 5), as well as a desktop computer running Windows XP SP3 dualbooting Ubuntu (which I don't really use), and also a VMware XP on the side. I'll be getting a laptop soon with Windows 7, at which point I will begin using Windows applications related to network and computer security, such as Cain & Abel and others.
The laptop isn't the best, but I got it for free to mess around with Linux so I can't really complain. It's a Celeron M 1.5ghz (haha) with about half a gig (500mb) of memory and a 40g harddrive, which is good enough to run basic pentesting and password cracking.
My desktop is running XP has a 250g hard drive with two externals connected (one at 1tb and another at 500g), a 2.8ghz dual core CPU, 4g of memory (only 2.1 usable, since I'm using 32bit XP), with a 9800gt Nvidia GPU.
All in all, I'm happy with the specs I have, but sometime in August I should be getting a good Windows 7 laptop better than my current desktop and should be dual booting Ubuntu Backtrack5 and Windows 7.