Windows 8.1 Upgrade and PAE, NX, and SSE2

I have a 6 yr old Dell Dimension E520 currently running Windows 8. I tried to upgrade to 8.1 but have been denied because my processor doesn't support PAE, NX or SEE2. I've read some posts that stated that this was an issue preventing them from installing version 8. It wasn't an issue for me since 8 installed. My questions are why would this effect me now and is there a work around?

Welcome to the "old CPU club." Follow this thread for progress reports and it will also "attempt" answer all of your questions.

http://www.eightforums.com/installa...ys-won-t-work-pentium-4-prescott-630-a-2.html