OK, that information is helpful.
First, are your backups made via Time Machine?
Secondly, it looks like the RAM has been upgraded from 1 Gig to 4 Gig. Third, assuming it has the original hard drive, that would be a 9 year old 320 Gig 7200 rpm drive. Being 9 years old, that could be the issue.
Now, since you are using OS 10.8.5, and assuming the Recovery HD partition is on the hard drive, you can boot to that partition by holding down the Command and R keys. This link describes what is on that partition:
https://support.apple.com/en-us/HT201314
You would then select Disk Utility, and it will run more extensive tests on your hard drive. It would be best if you run Repair Disk at both the Volume (ie, top) and Partition (ie, secondary) levels. If Disk Utility tells you there are "major" issues with your hard drive, then you would need to have it replaced.