I had a very similar problem when I bought my asus dual fan 4890,
loud fans at start up,beeping and signal sometimes @800x600 and other times none whatsoeve.after exhausting all the options I took it back to my local pc component shop,he gave me a new card,same result..so we tried again with a nvidia card..same result,ended up being my pci express slot was faulty and my board blew in the end (must have loved my 8800gt too much ) needless to say I got a new mobo and it all worked first time.
might not be the same with you,just thought i'd share my gpu nightmare
loud fans at start up,beeping and signal sometimes @800x600 and other times none whatsoeve.after exhausting all the options I took it back to my local pc component shop,he gave me a new card,same result..so we tried again with a nvidia card..same result,ended up being my pci express slot was faulty and my board blew in the end (must have loved my 8800gt too much ) needless to say I got a new mobo and it all worked first time.
might not be the same with you,just thought i'd share my gpu nightmare