Pianoteq 5.7 compatibility with Win XP?

According to the website, Pianoteq should be compatible with Windows XP. I use Pianoteq all the time and with no problems on my (main) Windows 7 machine, however my attempt to install the program on a fresh installed older WIn XP machine did NOT work: The installation/ *.exe file would not even open.

Could it be that Pianoteq requires some component being installed on XP (32bit) or may it just be that it is not compatible - despite advertisement?

Thanks
Bernie

EDIT and solved: I had to install Service Pack 3, not only SP2. Now it is working :-)