Will try to put in more info on this discussion. After 2 days (couldn't get a cursor), I finally partitioned my iMac (27") Yosemite and did as it suggested, which was give 20 gb to the partition. I used bootcamp. So, after getting Windows 7 Home Premium 64 bit into the partition, I found out all the space is gone! I tried to put in an antivirus and had no room. I have not installed anything in the partition other than Windows. I went back into my Mac and looked at the disk utility but it is greyed out and won't let me resize. Tried looking for info online, but there was only an extremely complex solution (seemed to be to do with the registry??) and I am not computer literate enough for that. If I have to start all over again, will Microsoft allow me to put back the Windows I bought? Thanks.