Is this the first time you've noticed two explorer.exe's? Try looking again right now with Process Explorer, without any other windows open. Is it still there? If so, double click on its entry in ProcExpl to bring up its properties. The path
should be C:\WINDOWS\Explorer.EXE
(unless you have Windows installed on a drive other than C:\, in which case replace C:\ with the appropriate drive)(See the image below). If it's not listing C:\WINDOWS\Explorer.EXE as its path, then we'll need to investigate it very aggressively.
If there is only one Explorer.exe process listed, then I'd wager that what you saw was merely a fluke; an instance of Explorer.exe that didn't die when it should have (hey, it happens).
As for the Explorer.exe process listing its current directory as C:\Documents and Settings\username
, that's okay, it's designed that way.