Kudos! I pulled the PSU from another computer and tried it... Works just fine now... I've had a few PSU failures over the years, but never with symptoms like this... too bad I didn't have a spare PSU to try first and save myself a couple of hours of troubleshooting time...
I don't think that would be a problem. Using a Dell installation disk.. so long as it reads a Dell BIOS I think you can reinstall without a new OS license... (Of course to swap the HDD into a different computer and have it work, the original and new computer would likely need to have the same mobo and BIOS... And guess what!! All of the T3400s apparently have that.. so you CAN swap HDDs between them at will so long as they have the same video card...)
No worries friend. I am keeping this link in the inbox since I learned some things that will benefit me in the future.
Well what do you know. Glad to hear it worked out. I would've likely tested the PSU with a DVM, but swapping is always a good method if you've got a spare. The last time I had a PSU die, it got a surge that went right through the surge protector and it was dead as a door nail. On top of that, it can be misleading to pull out and test, because you have to short certain pins on the connector to enable the supply.
Some have chimed in with "I've had lots of trouble with Dell PSUs"... Well, I've had several Dells.. and for years... this is my first PSU problem in a decade... Makes me think that some geographical locales with erratic power may influence PSU failures. If thats the case, so be it. However... anyone who has a Dell PSU failure, should look to replacing it with a perceived "quality" unit.. not some $29 el-cheapo from Best Buy. (I'm not suggesting Dell PSU's are of low quality... I've had many units and never had a failure until now... and this was on an "el-cheapo, Vostro".... not a quality workstation machine. In fact, Dell's PSUs have been average, or better) Corsair is a good replacement candidate... they get good reviews from enthusiasts.. apparently are made for Corsair by Seasonic... which is a good thing.
Dell was famous for a long time for utilizing older parts in their hardware, resistors etc. Of course this was done at the mfg/ supplier but Dell must have approved it. I took a blown resistor out of a Dell CRT once and tried to replace it, it was a part used in radios and hadn't been used in 5 yrs. The CRT was made in Mexico. So u never really know what you have inside depending on where hardware was sourced from. Another example , when Samsung 19" wide screen flats first came out and were all the rage I had a bunch of them , some of them just weren't as bright and crisp . After looking into it I discovered the ones assembled in Singapore were great and the problem was with the ones assembled in Mexico.