You'll want to check Compaq's website and try to find a motherboard manual or something similar. There might be a chance that there'll be a jumper that will disable onboard sound. Also (FIRST) check the BIOS setup and see if you can disable it there.
Be warned, however, that Comaq machines, especially that model, are bunk. We have a 4505 here at work and I've had nothing but trouble trying to support it. I even had to completely wipe the machine and reinstall a fresh version of windows to solve an odd problem a while back. It still has problems every now and then...in fact just yesterday I had to reinstall the network drivers. Fun stuff!
Not to mention dirt shit performance. AND I also think that they're limited to 1 PCI/ISA shared and 1 ISA slot if I remember correctly. You better make sure that a big sound card will fit in there.
Sorry to be so negative but of the 15 or so machines that I've bought for this place, the name brand computers are the worst. The HP sucks, the Compaq sucks, and the PB sucks. They were purchased when I was young and stupid
Just don't expect much. The cards you are looking at are nice, though, and can be used in your next machine. I would consider building yourself a decent workstation. This can be done for around 500 dollars and up. (minus the fancy soundcard) I know that you don't want to hear that....but what's the point of sticking a wonderful soundcard into a machine that's going to give you nothing but headaches? (And you will have them)
Case, ps, keyboard, mouse - $100
Mobo w/ ATA66 support - $130
PII-450 CPU w/fan - $120
4MB cheap video - $30
13GB ATA/66 7200RPM HD - $130
64MB PC100 (generic) - $65
Floppy & CDROM - $70
17" Monitor - $230
= $875. Just add your favorite soundcard.
Note that you don't want to keep your existing machine you can use the floppy drive, the CDROM, the mouse/keyboard, and the monitor...so your new price would be:
$535. Roughly of course. It's not that expensive to build a machine for recording. In fact it's much less than the adds you read in the paper for multimedia PC's. Remember, buy cheap upgradable components, then upgrade when it's cheap. The PII-450 is cheap now, and if you buy the right mobo, you can upgrade to a PIII-800 or so when they're cheap! Consider it.
Slackmaster 2000