turn monitor off and computer off. then turn monitor on, then computer on about 2 seconds after monitor is on. also check connections to monitor, mine was not plugged in first time, check both power connections to mother board and the power to vc. if u see the lights on on your mobo, there's there's a good change card is not hooked up to monitor right.
if you had to remove the mobo to install cup and fan, then make sure all the connection are on correctly. the above suggestion is how i solved mine last week when installed the 465 for the first time. but changing cpu and putting old one back and nothing happens, there's a chance one of your connection is wrong. make sure vc is properly seated (mine was not, lol), also switch cables to monitor to something else, vga etc. last make sure the selection on your monitor toggle to find the one that it recognizes.
hook up your ps3, wi to your monitor make sure it works too.
semp