I would like to know what you would do if you were in my size 12's.

I have an HP desktop PC that was given to me this summer under the guise that the OS as corrupt and the previous owner wanted to just buy a new PC rather than deal with it. (the warranty ended last April) The PC isn't a slacker - it's got a 3.2Ghz CPU.
I stored it in my (dry) garage until about 6 weeks ago. At that time I brought it into my office and plugged it in. I got a very brief "vzzzt" from the power supply, followed by a puff of acrid smoke. I immediatly unplugged it.

I looked on HP's parts site and found that they no longer stock the power supply, but to call. I called and was referred to a third-party company who is authorized to sell OEM-quality replacement parts. Last week Monday (the 5th) I ordered a new one from the vendor and paid extra for 2nd day Air delivery. They finally shipped the part at 7pm on FRIDAY! It arrived on TUESDAY of this week. (that's not what I call 2nd day air)

I put the new power supply in, plugged it in, and pushed the power supply button. Now I get a red LED that blinks 4 times. According to HP, that means either something isn't plugged in correctly (something my 10-year-olds could do), or the system board needs replacing. What I find very curious is that the fan on the back of the power supply NEVER starts to spin. I chatted with HP and they suggested taking the PC to a local HP service center.

Would you:
1) return the power supply for a replacment
2) take it to the HP Service center for further diagnosis
3) just buy a new system board (~$275)

Thanks in advance.