If your mother board is like a All-in-Wonder board look to the rear of the board and you will see 4-5 black or brown "slots" with a lot of connectors in them. These are PCI slots and you can plug in your new sound card to one of these (remove the knock-out plug to the rear) and then start the unit. DO NOT plug it into the top one--this is a AGP slot and it won't work!! Plug your speakers and microphone into the new sound card and not your old jacks.
After it starts, XP will notify you of new hardware detected and ask you what you want to do. However, if it is Windows certified, it may just tell you it detected it and wait for you to tell it what to do.
Agree to everything.
Now as far as the old drivers, Go to start, settings, control panel, add/remove software, find your old drivers for the old sound card and remove it. Or, in control panel, go to add/remove hardware, and remove your old sound card. What your trying to do is tell Windows to not start the old sound card.
If, however, the new drivers prompts you to override the old drivers, great, do it.
I know this all sounds confusing, and it is. I have no way to know how your unit is configured and this is why shops charge so much to do stuff like this.
Is this unit within a LAN? If it is, the topology type would help me understand how your set up. Are you using a router and a NIC card? Server?
If it gets to far out of hand, go to a local comunity college and ask if one of the CIS classes would be able to set it up as a project. Or, talk to the people who sold you the card. If you lived within driving distance of me I could do it for you.
I know I may be a little vague here but it is very hard to know how your set up. Quite often I get calls from folks who buy stuff off the web and don't have a clue how to install it. Then they get mad because it doesn't work. It's not the sellers fault nor is it the buyers fault. There is just too much to take into account when changing hardware or software.
Oh, one more thing. Make sure you save all the info you need to save when changing the hard drive 'cause it's all gone when you pull the old hard drive. Or if you have a Null Modem you can dump it back in.
Are you ready to take that college course yet?
Dave