hi man
i also had the same exactly problem with matlab and fortunately i
managed finding a quite easy way to solve it.
1)open your pc and while booting press F8 to boot in safe mode.
2) then choose to log on with the administrator account.
3) insert the cd of matlab and install it.
4)CAUTION! after installetion don't start matlab!!!
5)restat your pc and boot in normal mode (start windows normally).
6)log on with your account
7)go to c:\MATLAB7\bin\win32 and find the ''MATLAB''
8)send shortcut to the desktop
9)and
10) !HAVE FUN YOU DUDE! ;P