If it seems like it's going to fail, you might be wise to back up everything important while you still can. A portable hard drive is usually the best option.
You should be able to run memory tests and scan the disk drive through Windows. (What version do you have?)
As for the hard drive, in order for everything to run as it ought to, you should ideally have 10 to 15% of your drive capacity left free. If you fill it up, your computer will slow down.
I'd say run some more scans and fix any bad sectors on the disks in your scans, and it might solve the problem.