It being a Dell it probably has the sound card with the imput already, and you just need the patch cords.
You can get them at wal-mart.
They're called Stereo "Y" Adapter, and made by Philips.
but with the specs;
Mein Computer:
Dell
Windows 2000 Pro
400MHz Pentium 2
64MB RAM
20GB Hard Drive
I would think you'll have problems, that's a pretty slow processor, you'll probably get pops and skips when you start burning, not to mention that Ram, and that HDD is a bit on the small side to be working with a lot of music.
EDIT;
I misread your post, I thought it was music you wanted to do with that computer, which itself would be tough, DVD's are almost out of the question.
Good luck trying that one.
Probably take like.... a week to burn a dvd on that thing.