Unable to start - please reinstall the base game message? [SOLVED]

I have a retail download copy of the sims 3 and installed some expansion packs via torrents. I have read the thread here on how to install the sims 3 properly and followed all the instructions and used the ultimate fix. However, when I try to start the game I get the following message: "Unable to start. Please reinstall the base game". What do I do? If I reinstall it - will the torrent expansions still work? Does anybody know why I get this message?
I haven't played the game yet at all and have no custom content etc.

If anyone can help I would be reaally grateful

//EDIT

Oh, and I have it all installed on an external harddrive..if that has anything to do with it

//EDIT

I was able to solve it - turned out it was because of my external
harddrive. When I installed it it was (E:) and when I got the error
message it was (F:) I simply changed it back to E and it worked (now I
have crashing problems...but this is solved!)

Admin edit: Please use the "Edit" button on your post, instead of double-posting. Thank you!

- ADMIN

//MOVED
Hello,

Glad to hear you solved the problem yourself!
Please let us know if you need any more assistance!

Ps. You might want to try THIS for the freezing/crashing.