My itunes wont download correctly. Please help!

So this is the story. I was running out of space on my :C/ drive. I have a buttload of music so I though to myself, Hmm...... I have a :D/ drive with 400 gigs on it I will move all of my music over there. SO I did that. But without thinking I forgot that my itunes music file was in My Music file and it transferred my whole library to the :D/ drive. SO when I go and click on Itunes nothing was there. SO i try putting all my music back onto itunes. I have alot of music and it kept on sayin I only had 243 songs on my library. It wouldnt add any more or delete any. SO I deleted itunes altogether. I tryed to redownload it at the website and when I open the setup it tells me "Could not locate :D/itunes". I have tried everything I know to try to get it to work. If anyone can tell me how to fix it please let me know. Help please!!!! :'(