It depends. YOu need to investigate and see what's there. if the folder is in your Local Settings/Temp Folder, chances are it might be archived MSIs (widnows installers).
You can delete them without any serious consequences......but the reason that they're there (if that's indeed what you're referring to) is most likely to aid you, the user. IE, when I create install packages, I set a flag to copy the entire MSI over to the temp folder and leave it. Thus, the next time a user runs remove, or repair they're not prompted for the cd in most cases.
You can also look at the .log files that are in there. In those log files there'll be an entry called product code (it's a GUID). You can do a registry -search for that product code and see if it even matters.
If it's another folder, then all the above is fluff anyway.