Macbook won't log in to desktop

My friend installed some maintenance software onto his Macbook and since restarting it, it wont log into the desktop. When he powers it on it takes a while before it gets into the login screen. After he enters his password the system just hangs with the desktop background and no dock. Possibly this maintenance software has screwed up a few files within the system. Any ideas?

OK first thing - before you get help we need to know what OS - what was the maintenance software? More info generally equals better quality help/advice.

Sorry, long time since I posted on these forums. It is running OS X 10.6 and the software that he installed is called 'Maintenance 1.3.2'.

Here is a link for the software:

http://www.macupdate.com/info.php/id/16790/maintenance

In that scene my first step would be to download and install this.

Tried resetting the PRAM, now the system is just hanging on the grey screen with the clockwise thing just rotating.

If the Maintenance program wasn't actually run, just downloaded/installed, then it could not be the culprit.

Could just be coincidence there.

Managed to get the Macbook to boot into Safe mode. He did a back up of the files he need. I deleted the Maintenance software then verified and repaired disk permissions while in safe mode and then restarted the Macbook (to allow for it to reboot normally) It took some time before it finally got in to the desktop,but it was running slow and felt quiet sluggish.

He has BootCamp (running Windows 7) installed on the Macbook. Is it possible to reinstall the OS X partition without affecting the Windows part?