If the computer is freezing up, then it needs some diagnostic testing and perhaps service.
It may start up OK in Safe mode, then you may be able to try testing to see if the hard
disk drive is too full for the system to function, among other items. It also may have issues
due to age; as hard disk drives fail. Resolve the problem before trying to hide the trouble.
If the computer was equipped with an install-restore DVD for the same system running in it,
that could be used as a boot disc, to try & repair the hard drive; at some point. You could
also erase and reformat the hard drive, if you have all of the correct software to restore it
completely; if not, then you should seek the install media discs to best restore software.
(And test the hardware for potential causes of trouble, such as worn HDD, etc.)
Then, if the problems are worked out, and the computer repaired to working order, it may
be able to be upgraded to a newer OS X. If it didn't include OS X 10.6. on retail DVD, that
retail install disc is about $20 purchase from online Apple Store. Then, it may be able to
find 'update' via the Software Update selection under Apple Menu, to 10.6.8 as download.
The unit may be in need of a RAM upgrade, plus a new larger capacity hard drive. And
the clock battery may be worn out, too.
In any event...
Good luck & happy computing! 🙂