spyware issue

Hi everyone, recently I have been thinking that I had spyware or adware or maybe even a virus on my laptop as my memory usage was starting to fill up without me installing new programmes or downloads. concerned as i was, I did a windows defender scan, eset smart security 4 and a spybot search and destroy scan but to no avail. So I downloaded a thing called spyhunter and it said it detected 6 spyware files on my system. but I can't remove these as it is only a trial version and don't have the 29.99 that they are aking for at the moment.
Anyway, how do I find out if this threat is real? and are there any good free spyware/ virus programmes out there that I can trust as the reveiws are very very varied?

Any help would me very much welcome!
I dont understand how some programmes pick faults out when others can?

Thanks in advance

 

Programs that claim you have viruses and then ask for money to remove them are usually scam programs.

 

so are you telling me the likleyhood of me having spyware or the such are remote and that it's just a scam to get me to by their program?

 

99.9999999-----% of this.

cheers ...