I would suggest you to don't go back.
If you haven't already applied the Service Pack 1, then I would strongly recommend you to install it now. Give it ago.
Just wait couple of more months and apply the Service Pack 2 as well.
By the way, everything depends on how easy it is for you to backup your two-year worth of documents.
What are your hard disk configurations? What processor and amount of RAM you have?
Normally, applying a Service Pack give a refresh to the Windows System files and makes Windows run faster. So I would suggest you again to install Service Pack 1.
All the Best,
McoreD