You may wanna try closing background task in the task manager window. Click on processes tab and sort the items by owner (or whatever the name of your PC is) click on each item to close. You will be prompted that terminating a program will blah blah blah, so just confirm. NOTE: do not close out explorer.exe or tskmgr. Once you restart your PC, those items will reappear.
If that still doesn't help, then consider taking the game back for an exchange like the other poster suggested. I play TS2 w/EP's and this is an ongoing issue with the university EP. If you use custom content or hacks, you might also wanna remove your downloads folder from TS2 folder and place on your desktop, then attempt to install uni. Over on the sims 2 forum, many folks have solved this problem by doing the above.