Ok Dwizzle, your Dad's pc seems to have a good spec, more ram than most of us have, but it will gradually slow down if regular maintainence isn't done on it.
It doesn't have to be complicated, the software is better now than ever, and mostly free. I tend to rely on CCleaner from
www.piriform.com, and also they do a very good program called 'Defraggler', well worth running. My current favourite defragmenter is;
http://www.auslogics.com/en/software/disk-defrag/download/
where you have a choice to defrag and optimise the hard drive at the same time.
As you have CCleaner, run the top 2 options on the left. Use it exactly as it downloads, and don't be tempted to tick all of the options in the empty boxes, it could take a very long time to run. (typical cleaning time 1 or 2 minutes).
Lastly, run CCleaner first, then the defragmenter. Repeat once a week.