bob1286, here is an important detail you need to clarify.
The computer, a T3400 , was working fine with an older version of Windows? Which Windows? **
The Windows 7 OS you are wanting to install is a retail version you bought for hat computer?
If you answer 'NO' to either of the above, it becomes a guessing game as to what went wrong.
You say that the Windows 7 home version works? OK, just stick with that. For any older PC there is little resewn to use a more expensive version of Windows 7.
Why do you want to use that old PC?
** That Dell PC sells for : US $199.20 on eBay and has a warranty and a real legit version of Windows 7. At an earlier timed Windows 7 pro was near to tan that price level. A few retailers still ask $199 for Windows 7 pro in a retail package.