Having problems installing win 8.1

I'm running win 8 pro, and I've been trying to upgrade to win 8.1, but it's not working at all. It will get to 95 percent installed, then a popup window will say cannot finish installing windows, then it restores the previous version I was running. Has anyone heard of this or has it happened to anyone? Thanks

What Anti-virus are you running? If it's not Windows Defender, turn it off or uninstall it and try again.

I'm running NIS Norton internet security. I'm not getting any messages from it. It downloads, and it get up to 95 percent installation, then aborts, and restores the previous version.

Is this a OEM manufacturer's PC with Pre-installed Windows 8?

No. I built this thing two years ago.I had win7 pro, then when 8 came out, and it was stable, I purchased the pro version of 8

Check the manufacturer's web site for up to date for Windows 8.1, than try installing.

manufacturer of what? I built this comp. There is no tech support

I'm assuming you bought the Windows 8 Pro as an upgrade and still have the product key?

If so then another method, if you have everything backed up and don't mind reinstalling everything (because it will wipe the partition), would be to try a clean install from the 8.1 ISO.

If it still works, you should be able to get the 8.1 ISO using this trick:
http://www.eightforums.com/installation-setup/33164-how-download-windows-8-1-iso.html

Assuming that works, then to get the 8.1 ISO to install, you initially need an 8.1 Product Key (see here and especially the Note on post 1) but then once it's installed you should be able to get it to activate by entering your Windows 8 Pro product key.
http://www.eightforums.com/installa...retail-windows-8-1-windows-8-product-key.html
You need the original Windows 8 Pro product key from the email when you bought Windows 8 (or in the box if you bought it boxed). If you've installed Media Center, the key you need may not be the one active on the PC itself at present so won't be visible with key readers.

Backup first before trying this though!

I bought the full version of win 8, and yes I still have the key. It's alot of work, but it sounds like I have no choice. Thanks for your help.

Depends what you mean by the "full version"?

I think the download process described will only work if you bought the Upgrade edition of Windows 8 Pro, which was used to get from XP/Vista/7 to 8.