Run the updates then try again.
You may also want tp do a permissions repair Applications>utilities>disk utility, select your (her) volume from the left column, First Aid tab and click repair permissions, after that run verify disk to make sure there are no disk errors (the erors will be in red font) if you get diak errors, you will need the install disk to repair it before you can do the upgrade.
Also make sure the machine supports the OS.
Try starting in safe mode and then try to run the updates, use an ethernet connection if available.
Power on the MBP holding the left SHIFT key untill you see the progress BAR, then release the shift key (note that this start will take longer so be patient) log in and try to run the software updates. If sucessful log out and restart normally. (note the logout and shut will also take longer)
If no joy.
Then check the disk/permissions.
Seems to me you need to first .....
Thoroughly check the details in the link sanpamjet gave you. I'll repeat it.
If your machine qualifies, bring it up to the maximum level for the OS you use. That is ...
Then follow up with software updates to pull in the iTunes and security updates. This should set you up for further progress.
All being well, you can then go directly from Snow Leopard to Mountain Lion via the App Store, providing you meet the specs.
MAVERICKS Tech Specs Apple - OS X Mavericks - Read the technical specifications.
Be aware that although Apple suggest 2GB RAM, the general concensus here is that 4GB is needed. And that any PPC apps you have will be rendered useless by the update.
A brief update. My post contained a small typo. You can go direct from Snow Leopard to Mavericks providing you meet the Mavericks criteria. Here is a link which will show you which apps will work with Mavericks and which won't. Can be a costly move and Snow Leopard is a very reliable OS. I would be inclined to wait a month or two, let Mavericks early problems be resolved by others.
Thank you for the star.