1. Reinstall the drivers by uninstalling the old ones...maybe update them as well if you don't have the latest.
latest 5200 drivers
2. Failing that, try a different monitor, which you did was the problem identical?
3. Re-seat video card
4. Try a spare video card...hardware may already be faulty...fx5200 agp...so maybe a quick ebay upgrade.
There's more steps if you feel advanced enough too, like maybe making sure the thermal paste on the gpu is good, checking for cracks on the soldering etc etc. Personal story: I found a site just browsing the web about people who have fixed their cards by "cooking" them, my screen went corrupt so I thought the card was scrapped. No harm in throwing it in the oven then...Then guess what happened afterwards it worked again. :) Youtube or google it.
Truth can become lie, but if lies become truth we're in trouble.