XFX Radeon HD5770 Grey screen, no video

Hello all

my pc specs are :-

CPU- AMD Phenom II x4 965 3.4Ghz "Deneb", Cooler = Cooler Master Hyper TX3 EVO
MOBO- ASUS M5A97 R2.0
PSU- Corsair VX550W
RAM- Kingston 2GBx2 1333MHz DDR3
OS- windows 7 32bit
ATI Drivers dec 2012


i have been using XFX HD5770 for more than 2 years,
been gaming for months...was smooth and without glitches or any kind of problems.
was using it in WinXP,
now Win7.

but i noticed a difference in temperatures of 5770
in WinXP Idling it was ~40c and goes upto 70~80 When gaming,
in Win7 idling it remains 50c constant and when gaming it goes upto 90c.
i dint bother much..i thought its normal..

but yesterday as i was playing for more than 2+hrs (first Arkham City [Love it!!   ] , then ARMA 2), it should up artifacts, a lot of flickering, pixellation (purple dots),and Grey screen with lines
then the pc got crashed during the game,
i panicked..restarted the pc,
but now its showing no video/signal to the monitor,
GPU fans are spinning by the way,
& when i touched the GPU copper pipes after it was switched off, it was very hot, a lot hotter then usual,
and keyboard num key light was ON, Caps lock was NOT working.

this is the first time anything like this happened, cause i play for hours (crysis, crysis 2, GTA 4, AC3 etc), and nothing happens !

so i tried the usual steps,
clean RAM, Replace
Clear CMOS, remove, Replace after a few seconds
retried...same


i tried a old backup graphics card (ATI 128MB) {Cause my MoBo doesnt have onboard VGA}
pc booted up, no problems with that
so i guess its the GPU..

no i cant turn it on using my HD5770
shows up No video, signal or anything....
its driving me crazy  

is my GPU dead???

Thanks in advance