All of the answers depend on how much of a budget you are on and what your recording needs are.
If you're on a really tight budget, a SB LIVE! card will probably do OK. Personally, I prefer Turtle Beach cards because I've always had the impression that they concentrate on sound quality more. (I admit it's not a scientifically arrived-at impression. I never really compared them.) But SB Live! is more of a defacto standard. There's an article right here on this site that discusses how an inexpensive sound card can actually be OK. Here:
http://www.homerecording.com/digital_results.html. Also, consider how many tracks you might want to record at once. I think the SB Live! can probably only record two at once.
You don't necessarily need a 7200RPM hard drive. I think a lot of people will tell you that they use a 5400 RPM drive. But it depends on how many tracks you want to be able to play and record at once. I couldn't give you an equation relating disk speed and the number of tracks because there are several factors involved. Any one might be the bottleneck. The number of track might depend on CPU speed, efficiency of the software, disk speed, or other small things. Also, 7200 RPM may not mean much if the particular disk doesn't have a fast data transfer speed. I've seen a comparison where a 5400 RPM disk was just as fast as a 7200 RPM disk because the 7200 RPM disk had a slow interface. Even though it was reading the data off the disk faster, it couldn't deliver it to the CPU any faster. In addition, you don't need to have a SCSI drive. SCSI is better, but more expensive. EIDE is fine. Me, I use a 7200 RPM EIDE drive.
I think a 600 MHz Celeron should be OK. I use a 450 MHz PII and it works great. But again, it depends what you want to do. More CPU power will let you use more or better plug-ins like reverb, compression, and EQ. One thing you want to consider is the floating-point performance of the CPU since recording applications usually use floating-point to do calculations. Since Intel CPUs have always had better floating-point performance, I've always recommended them. But there's an article over at ProRec now that indicates that may not be the case anymore. See:
http://prorec.com/prorec/articles.nsf/files/FA57D6CCC4004959862568EA001CAE54. So you may be able to save some money by going with another brand. This article may also give you some idea of what a particular computer can handle in terms of number of tracks and plug-ins.
I don't think the CD-ROM is critical. You can get a CD-RW for around $150 I think. I haven't priced them lately. I bought a Yamaha 4x4x16 CR-RW for $189 about half a year ago and it's fine. I'd definitely get a CD-RW as opposed to a CD-R. It's worth it. In fact, I don't know if they even sell plain old CD-R drives anymore.
Regarding video cards, if you have a choice between PCI and AGP interface, get the AGP. This will take some of the load off your PCI bus and leave more room for audio data.
I don't know about motherboards, someone else will have to answer that. I usually buy and recommend Dell computers. But if you're on a budget you can probably save money by getting something else.
In general, playing the budget-balancing game might be tough. You could save $100 by getting a slower computer and put that $100 toward getting a better sound card than SB Live! That would be a good choice if sound quality were more important to you than a ton of tracks or plug-ins. If plug-ins are important to you but lots of tracks are not, then you might save $50 on the disk and put it towards a faster CPU. If you do other things with your computer besides recording, then that might be a reason to devote more money to the computer.
(and a broke student). I desperately need some gear recommendations/tips for my planned BUDGET setup. I use it for HD recording, ACID, Cakewalk and so on. Here goes:
