Hi buttercupxs
If it's the Power Chute program that's associated with UPS power-backup systems ("UPS") -- then here's a link:
http://www.apc.com/products/family/index.cfm?id=129
On that webpage, different versions are listed for different UPS devices -- you need to match the UPS that you've got.
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If you are not using a UPS system, then the apcmain.exe file is generally associated with the "Ascentive Performance Center" software, which has a dicey reputation & can prove difficult to uninstall. If you are certain that you actually want that software, you can get it from their website (ascentive.com).
If you need to get rid of the Ascentive software, try the latest version of SpyBot with its most recent updates. (Malwarebytes AntiMalware is quite good at removing it, but alas -- there is no version for Windows Me).
Best of luck
. . . Gary