I wouldn't use Win2000 when you can get XP. I only used Windows ME (which is based off of 2000) because it came with my computer and was familiar with it. However, XP is a bit more stable than 2000 and soon enough 2000 is going to go the way of 95 and programs are going to stop supporting it. Given that you're currently using Win95, I'd suggest upgrading to XP as that will be supported longer than Windows 2000.
Also, all new computers come with XP, I don't think you'd find any except 'hand-me-downs' that use 2000.
For harddrive size, what do you use your computer for? If it's just for word processing and surfing the internet, 20-40GB should be more than enough. (Most box computers that you buy at the store come with 40GB today.) Manufacturer shouldn't make much of a difference - to me, they all seem to work just the same although some are faster than others.
For memory, I'd suggest 256MB of RAM. Yes, you can do well with 128MB of RAM, but applications are going to start requiring more and more as they get more complex, so it's best to get what you're going to need now instead of buying and then needing to upgrade anyway. Also, XP seems to run a bit slow with 128MB of RAM once you start adding applications to the system.
Video drivers - if you're not playing video games, a video card that's integrated to your motherboard should be ok, or you can get a 32MB or 64MB video card. If you're doing video games, I'd suggest at least 128MB - you can get them fairly cheaply right now and, as with the RAM, I think it's best to be a little proactive so you don't have to upgrade in a year.
_________________________
"Without the darkness, how would we see the light?" ~ Tuvok
Editor for Television Category