I have had problems recently with this computer freezing up.  I did a system restore, and it worked Ok for a day, but now when I turn it on the computer gets stuck just showing the numbers 3 & 4 on the tower itself.  It won't even bring up a display on the monitor. I think it may be time for a new computer.  Any suggestions?  The computer is 10 years old.

bensuncle

Diagnostic Lights x-x-3-4 usually indicates a memory issue, first try opening the case, then remove and reinstall all the memory modules, to see if this makes a difference.

See pages 19 and 41 Here:

  http://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_dimension_desktops/dimension-e520_service%20manual_en-us.pdf

 Bev.    

The OP has a Dimension e520, that requires a Dell OEM BTX motherboard, not a Vostro 260 that is ATX.

Bev.

Lots of Vostro 260 system Boards available on eBay for less than $100. New desktops on sale or from the Dell Outlet Store at $200-250.

To try to fix them using heat, I recommend the oven procedure over the heat gun, as you really don't know where the potential problem is located and the heat gun could easily over-cook some part. Should be the last thing you try. Lots of videos on uTube. Good luck!

Oops. Must have been looking at the wrong post.

Lots of 520s available at ~$50.