dell optiplex gx-270

These had bad capacitors on a number of them: http://forum.osnn.net/showthread.php?t=83297.  You can try replacing them yourself if you see that they are obviously bad and you can handle a soldering tool: www.badcaps.net

Good point about the bad caps. The ones I've seen with bad caps had visible swelling and/or leakage. Inspect caps for signs of swelling or leakage.

I've also seen slimline GXs with clogged heat sinks and dry/cracked thermal compound.

they even sell the replacement cap's in a kit :  http://www.thecapking.com/gx270.html

Yes, check your heatsink air flow and thermal compound.

Most [if not all] SX-270 and GX-270 built before May 2004 had defective caps.
Those built after suffer from heat related capacitor failures.
[Slimline GX and the SX variants are the worst for this. Problem exists all the way into the GX-7xx models.]
Each 10c rise in temp reduces electrolytic capacitor life by 1/2. [It's logarithmic.]

One of the problems with the 270's is the air discharge horn on the CPU fan doesn't exhaust the hot air completely out of the case. That results in hot air blowing right on the VRM caps and MOSFETs and the air just recirculates inside the case without ever leaving.
The GX-280's (at least some of them) had an improved fan in which the air discharge horn was extended so the hot air bypasses the VRM components and actually makes it out of the case.
A GX-280 CPU fan assembly should fit a GX-270 heatsink as long as it's for the same case version.

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I work for a school system, and we *had* probably 500 of these in service at one point, until they all started going bad just out of warranty.  Check on your motherboard, around where the processor is and look at the capacitors.  See if any of them are swollen, if they are, then the motherboard has just died.... this was a major problem it seems for most all of the 270s.  The culprit most of the time is a capacitor with an X stamped on top of it, they swell the easiest, if this is not the case, get some base mounts and set them sideways, it seemed to extend the life for us.  Hope this helps.

Opps.
When I said GX-7xx I was thinking of the GX-620's I've seen.
They are having issues with the small 4,5,6 mm caps going bad.
I only suspect the GX-7xx has that problem. The GX-6xx does.

The heat issues affect ANY brand of cap.
I've seen these systems bloat and/or vent top of the line Rubycon MBZ and MCZ series caps.
The defective batches were using Nichicon HN and HM series caps which do have an X vent stamp.
- But MANY companies use the X shaped vent stamp.
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