No Problem
There should be no problems installing the new card in XP, make sure to turn off any onboard sound in your bios, and for the love of everything holy: If XP says the driver will not work and cause your system to basicly stop working do not click on the "Ok, install it anyway button, hold off , goto the manuf. website and obtain the latest XP drivers for that card. The major problem people have with XP is driver related if you install a driver that XP has warned you about chances are very good from that point forward you will have system that is as stable as M.e. and once the damage is done there are very few times it can be undone without clean installing the system. Exceptions to every rule. But heed those driver warning messages Microsoft means it when it says Cause your system to become unstable / unusable is some/most cases.