A1Click only deletes what you tell it to delete. It is fully compatible with Windows 7.
Please look in the Cleaner Settings to see what you have it set to delete. If, for example, you have checked the "Old Files (1999)" checkbox, then if you have a program installed that is that old, it will be deleted. A1Click does not have this checkbox checked by default, so you would have had to check it manually. Please look at the checkboxes and what they do before you check them.