Trouble updating

I have a 4th gen ipod touch bought new and used for about six months then put away for awhile. I pulled it out of storage last week to put some apps on that my parenta and friends have only to find I cant download any without at least ios 4.3. Dusted off itunes on the pc and tried the displayed update to iso 6 came up after two hours corrupt download. Tried two more times on two different days same result, tried the restore option same result. Tried a manual download, got a zip file itune couldn't read, extracted it same result. What do I do? is iso 6 to big a jump from the iso 4.2 on the pod or am I doing something wrong?