Hold on, what do you mean? You put in an OS X disc, and then you get a blue screen and what... it tells you that "Windows Server has crashed"? What has Windows Server got to do with an iMac and an OS X disc?
If you just bought the iMac and have never used it before, it could be that it has Windows Server installed on it. To be honest, I have no clue how to get it to run the OS X disc if it is starting windows.
The only thought I have is to download gParted and burn it to a disc, and then erase the hard drive using the instructions on there, before trying to install OS X again.
DO NOT do this until you have had ideas from other people though, as this might mess up your chances completely. Please wait for someone else to confirm. At least post more details and try and use punctuation because it is very difficult to know what you were writing about.