Windows 7 X64 Computer Slows Down On Opening MS Office 2003 Stuff

Whenever I open anything from microsoft office 2003, that can be outlook, that can be a word document, that can be a powerpoint presentation or an excel sheet, my windows 7 taskbar and the computer in general slow down considerably, but expecially the taskbar lags for at least 3 seconds whatever I do (like moving the pointer over several icons so that the aero-thingy shows up takes 5 seconds to pop up the little windows or opening a new explorer window). So when did it all start? At first everything was fine, office 2003 was running fine with w7x64, then I installed the cisco system vpn client (64bit of course) because i need it for university. After that the problem occured and I haven't been able to make it go away since then.

1. I uninstalled the vpn client -> no changes
2. I uninstalled office 2003 and reinstalled -> no changes
3. Office is updated with the latest patch -> no changes
4. I tried to turn of aero (who knows?) -> no changes

System in general:
CPU: Core i7 920
Memory: 6 gig ram 1333 tripple channel
HDD: 640gb western digital aals
PSU: Enermax modu 82+ 625w
Graphic: Geforce gtx 260
Mainboard: Gigabyte ga-ex-ud5