reset ipad1 to factory settings but cannot update to ios 5? any ideas please

If your iPad is currently on iOS 4 then you can only update by connecting it to your computer's iTunes ; if it's on iOS 5+ then you can either update to 5.1.1 via your computer's iTunes or directly on it via Settings > General > Software Update (that option only shows on iOS 5+)

Updating iOS : Update the iOS software on your iPhone, iPad, and iPod touch - Apple Support

WWhat do you mean by it doesn't appear possible? You have to explain what happens when you try to update. Are you using iTunes? WiFi? Are you already running iOS 5 and just trying to do the update to iOS 5.1?