Gabelvampir: Hmm that sounds a bit strange. You should try the following things, probably in this order:
1) Check if there really is enough disk space to install. The installer should do this, but double checking could help.
2) Turn off the Norton Internet Security, programmes like this often interfere with installers.
3) Check the filesystem of the partition you are installing to, and perhaps of the partition were you're system stores the temporary files (normally the Windows system partion C: )
If none of this works post again, maybe I'll think of something other then. And if something does work it would also be nice if you would write a short post about that, and mark the question thread as solved.
just verified, the problem is related to Norton...
