Computer died

[jack-rp9/bkPP+cDYtjvyW6yDsg at public.gmane.org (Jack Coats)]

you might try putting a 5 ohm 1A or larger resistor across the +5V to
provide some load.  Sometimes switcher supplies seem to refuse to work
without some load to keep the occilator doing some work.

Or 12 ohm 1A or larger on the 12V.

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For some low end commercially made testers...

http://www.amazon.com/HDE-Power-Supply-Tester-SATA/dp/B004J7BT28/ref=sr_1_2?s=electronics&ie=UTF8&qid=1301854122&sr=1-2
Looks OK, and under $10

http://www.newegg.com/Product/Product.aspx?Item=N82E16899705002&cm_re=power_supply_tester-_-99-705-002-_-Product
is about $15 and looks like mine, but that doesn't mean anything

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=2441812&CatId=1107
from Startech is about $12

Some local computer shopes may have some similar.

All plus S&H and Tax