What antivirus are you using (if you are using one of course )? Some antivirus doesn't like the UPX compression of PowerTools and causes problems with it (old versions of Panda coming to mind). Do you have another security program like an IDS (PrevX, WinPatrol...) or spyware protection in real-time or something on the same lines?
I use NOD32 for AV..that's all in the way of 'security' that and the firewall. I don't use the C: Drive for anything except windows, I use the 'D' drive for applications everything goes there. C: drive is kept pretty small under 800MB.
I could try a new directory in D: however I don't see that would matter as version 2005 did OK in it's present directory on D: and I just installed over that.
Must be something else..a weirdness one comes to expect these days.
I'll probably wait for the next build and see if the problem is fixed.
There's always the clearout and re-install then if that fails reinstalling the 2005 version for now..by the way, where can you get a copy of the old 2005?
S.