Tech Help...The Sims....(Dem?)

Okie dokie, I was trying to install an expansion pack, and it was taking awhile so I went and did something else and when I came back it had stoped and said insert disk two, but my mouse was froze, so I inserted disk two, and clicked enter and it finished loading. Then when it finished it said something like it now has to varify it's uploaded or something like that, but my computer was froze, the mouse wouldn't work and neither would the enter. so I had to shut it off. After I restarted it, thats when I noticed the problem, The exapansion pack is listed, but I Can't do anything with it, it wont open, and putting the disk back in doesn't help, and when I went to uninstall so I could reinstall it wont do anything,it's like it's listed but not there. ...Now what? How can I start all over again?