Hello everyone i recently purchased a computer...asus m5a88-m, 4gb ram (2), amd fx-4100 (quad core) processor, 1tb hard disk, but the performance is not up to the mark..after putting it for service, formatting the entire hard-disk and installing fresh copy of win7 i installed ati radeon 5450 video card hoping thar i can get the speed i want..but the computer hangs on startup screen...so i took out the video card and the computer works fine...what could be the reason..please help.