It could be that the Adobe Acrobat trial came pre-installed on your machine.
Best thing to do is to go to add/remove programs, remove Acrobat (and Reader if it exists) then try your install again.
It also might be a good idea to run the Microsoft Installer Cleanup Utility (I think they have a version for Win 7 anyway) and use it to remove any leftover pieces before trying the install.
I did just that, I went in and uninstalled my Adobe and reinstalled it.
It worked that time, thank you very much..............