iphone not restoring or updating

i am trying to restore/update my iphone, the first time it stopped halfway through with an error and now has gone into recovery mode the iphone itself is detected on the computer and tells me it needs restoring which i tell it to do, but its been preparing the iphone to restore for hours showing no evidence of it actually doing anything and on its screen it shows that plug and the itunes symbol, which ive already done, i have retried at least 6 times now, Any help?