OK, time to recommend a product:

I'll start with the basics, first. A sound card.
I already recommended it a few times before on other threads, but this is the official recommendation.

An affordable yet good sounding card/cards, comes from M-Audio.
If you're tight on money, yet still want to get a good sound card, they have the solution. they have several cards, depending on your budget, and on what you need. (usb, Firewire, PCI card etc.).
You'll find some cards with mic pre-amps too, so you don't need anything else to record a microphone. They have almost zero latency, and ASIO 2 Driver.

There are other good sound cards from manufacturers like RME, Logic, Digidesign, Mackie and even Lexicon came out with a new sound card for low budget, yet what they consider low budge might not be very affordable for a lot of us.

I myself am using at home 2 of M-Audio sound cards.
On my desktop I'm using the Audiophile 24/96. been using it for the past 2 years and very pleased with it.
I also recently bought the FW-410. an external sound card connected by Firewire to the computer. has MIDI I/O, 2 mic pre-amps, 8 analog outputs which allows you to mix for surround (up to 7.1) digital out and 2 headphones outs. It has great sound, and a very user friendly control panel.

If you choose to try them out, make sure you choose one that supports your operating system. Some of them only support WinXP/2000.