do you have a spare computer? cuz you may have to try swapping in another power supply.
Do you know what capacitors look like? like tiny miniature water towers, lol..but sometimes they swell and bulge on top...usually there are some power capacitors around the cpu etc...look and see if any of them are bulged on top or leaking stuff out of them.
look
here for an article on capacitors, with pics etc to show you what to check for.
Usually when you smell something it is from the power supply.