How to ger rid of viruses on my computer for free?

its says my RAM memory usage is crutically high and there are damaged hard drive clusters. how do i get rid of these problems? windows 7 repair wasnt able to fix the 5 detected crital errors. how can i get rid of this for free? its also says the system has detected a problem with one or more installed IDE / SATA hard disk. It is recommmended that you restart the system. i already restarted my computer