D00d, be really careful with these things. Did you choose Dynamic disk when using the diskmgmt snap-in? If you're a home user, ALWAYS choose basic. If you're running Windows Server 2003, its OK (?) to use Dynamic volumes.
What you need to do is boot off the WinXP CD, enter the Recovery Console and then format the dynamic volume (whatever drive letter you gave the volumes) and then restart and reinstall.
For more info, check out
this and
this
Next time, be careful.