Audio not coming through on new PC set-up

[ajp]

Hi.
Trying to set-up an Mbox with Pro Tools LE 6.4 on a friend's PC. I've been using Pro Tools for 4 years, but never on a PC and we are having some problems with the audio.
1. For starters, I set up a click track and the click is muffled and distorted. It sounds really strange.
2. Next, when I tried to record audio using an XLR and a a number of different Mics, I get no sound from the Mic.
3. Next, I tried to plug a guitar directly into the Mbox and the guitar sound comes through the speakers and headphones, but it doesn't register a signal within Pro Tools.
4. I tried to import in MP3 file to an audio track so I could at least show him some editing basics, but the MP3 file comes through all distorted and muffled.

- When I say distorted and muffled, think like how Charlie Brown's mom's voice sounds.


I know all the connections are fine and settings on the Mbox are good. I've been using it forever, but never on a PC. I've tried multiple mics and cables. I know it's something with the pc because i checked the Mbox with my Mac and it works fine. Something within the PC set-up is not allowing the audio to register in Pro Tools.

Here is is set-up:

Dell Dimension Desktop
Intel Pentium (R) 4 CPU 2.80GHz 2.79GHz, 504MB of RAM

Windows XP Home with Service Pack 2

PLEASE HELP!