That's a standard program to install Windows programs. It's used by Microsoft Office, for example.
Microsoft has a utility that cleans up left-overs. I think you can use it here, but you will lose the program it's trying to install now.
See http://support.microsoft.com/kb/290301 for a description and a download link.
I've been trying to sort out files to make more room on my computer. Have you ever heard of 'Windows Installer?' When I try to open some applications, a sign by Windows Installer, will tell me that it's preparing to install. It does but it takes ages. I've never had this happen before and I'd like to get rid of it. Please let me know if you have any suggestions.