So what is your PSU? The HD 4770 consumes about 50w during gaming, the HD 5770 consumes about 61w while gaming. Running something like FurMark will push the HD 5770 to around 81w. Don't know about the HD 4770.
Do not bold.
My PSU is a 550W great wall.a bit cheap but so far it has worked fine with my PC,thanks for your help.looks like the XFX 5770 will be ok without buying a new PSU,thanks again,Mrclownface!!!