Yeah, make sure you have Windows down to the BARE MINIMUM of processes (if you have anti-virus software and youre trying to record...), especially related to audio things. I always disable my onboard audio, usb, firewire, etc etc. (everything that is not essential that might get in the way) prior to serious recording. There is a way you can set up a different boot thing (forget what its called) so windows won't even load certain drivers or software if you tell it not to (and you select which boot you want when the pc starts up).
There are some internet sites around that will tell you how to further tweak windows xp for audio recording that can help a bit too.
This isn't really specific to your problem but every little thing helps when messing with a finicky computer.
definately reinstall your aardvark card (physically take the pci card out) and then reinstall it and put the driver you have back on. if that doesnt help, then try a newer driver version if there is one... if not sometimes the older ones actually work better.
You might try downloading a free trial version of some other recording software to see if you have the same problems.
hope this helps
