downlaoding apps on xperia x10

hi guys, i ned help, how can i download apps to the android market??? please help...but before anythig else, my xperia was rooted and i cannot unroot it again thats why i cannot download anything?? does this affect the downloading process? if the phone is rooted???

i already did everyting, format, reset the phone, turn it off, took out the battery and same everything, nothing happend it just went back to how it is..nothing happend, i cannot download anything from the market?? it only says start downloading but nothing.