Just upgraded our 2 laptops + Media centre from 2010 to 2011.
Bit of a problem on the media centre XP home SP3.
Upgraded and lost all USB ports, checked device manager and all drivers had the yellow triangle ! (code 39 or 41)
What a PITA due to having a keysonic wireless USB keyboard.
Took an hour to fix including going in the loft for a PS2 keyboard and trying to remember how to get around a PC using just a keyboard

been a while since I last went there.
You need to remove\uninstall KIS 2011 with the removal tool which is on the Kaspersky website and select
All
Known
Products.
Uninstall all USB drivers through Device manager, reboot, check device manager and still seeing the yellow triangle with code 39 or 41 uninstall all USB drivers again but before reboot re-install KIS 2011 enter serial, reboot and hopefully when windows restarts your USB drivers should install.
Modified slightly from this post
http://forum.kaspersky.com/index.php...post&p=1385781
Kaspersky removal tool
http://support.kaspersky.com/faq/?qid=208279463
Would have been so much easier if I also had a PS2 mouse