Im having a small problem installing xoops. at the beginning of the wizard i get
Directory uploads/ is writable.
Directory cache/ is writable.
Directory templates_c/ is writable.
File mainfile.php is writable.

But after i put all my server and database info in it says: Could not write into mainfile.php. Please check the file permission and try again. Im running iis and i know i don't have and permission settings. I can open mainfile.php in notepad and make changes and save them. Im not sure what to do.

Double check your permissions. 666 it should be then try to restart the installation...

You need to give the IUSR account modify permissions on mainfile.php