I posted the following on their forum and thought it might be helpful to post it here also: So I installed V3 free this morning using Upgrade option on a Pentium 4, XP, SP3 pc. The reboot was pretty bizarre! At least three overlapping GUIs were present that I could discern (there may have been more). Completely froze the PC, including the clock (never noticed that one before but maybe that always occurs). I then forced shutdown (memory dump occurred of course) and rebooted. Now all seems to be quite normal other than sanboxed sessions are taking longer to start but this might be because I've enabled loopback (NOD32 user, so thank you for this option!). Anyway, if you encounter any crazy problems force a shutdown and try a rebboot and good luck!