OK, thanks for the quick reply, I'll try that, how do you rescan by the way? Do you have to type in some commands? I'm not such a computer expert and I use windows 7.
Close Bitcoin. Go to start -> run (or press WinKey+R). Type this:
%PROGRAMFILES%\Bitcoin\bitcoin.exe -rescan
If it works, Bitcoin will take a long time to open, and the transactions should appear when it does open. This feature was introduced in the very recent 0.3.20 release, so you might not have it.