So just to be clear, you have tried the two search programmes suggested by Eric which failed to find the actual file itself (that would then indicate the file does not now exist - i.e. you may have previously removed it!), you then looked in the "Receipts" folder and discovered a ref to that file and deleted that and then finally you trashed the "InstallHistory.plist" file.
I wasn't advocating the deletion of the plist because I was not sure on how "System Information" uses that file or how it's created, but if that has worked and a new "InstallHistory.plist" has appeared you may have resolved your issue.
How the "InstallHistory.plist" is updated could be important, i.e. is it revised from the actual install process of applications or does it get it's info from within the "Receipts" folder - if it's the former you may have now lost some additional information about previously installed applications, looking at "System Information - Installations" should confirm if that is the case.
Eric, John and the others may comment on this, I certainly would appreciate some thoughts on how the file is created and if it's removal could have any additional consequences.