Faulty registry

My Computer dell inspiron 9300 with xp home is very slow to stat up and the cannot use any of the  menue for programmes, the colour of the bar at the bottom of the screen is white all very wierd. The only way to use anything is to  use task manager/file/new task. Suspect registry problem as I could not download from microsoft site. had errors went onto microsoft site and errors page took me to play with registry. Tried in Safe mode to restore but will not allow me even as administrator. I read somewhere there are files in system restore that take a photo of registry and you can replace??? As a lst resort can I repair my registry with out re-instal factory to oem original state??

Please advise ed