Computer has a bug & I want to "erase" everything (& reinstall my saved files)?

I think I have a "bug" on my computer bec. it is running extremely SLOW &my "your virtual memory is too low" keeps popping up (this never happens). I have 3 TOP spykillers& 1 virus killer(Norton) & still cant get rid of it, so I may have to erase my computer & start again. Initially it blocked all of them from working, but theyre working now but it's still slow.//I've worked in *internet on *internet off *safe mode. //It was blocking my Spware Doc & I FINALLY uninstalled it & did dwnld.anew and did find ONE spy (a keylogger I believe)// I tried to do "recovery" back to 2 wks ago,3 wk, a mo,2 mo, but IT wont do it. // went to Microsoft and did their malicious program ck. for 1-/12 hrs. &it didnt find anything. IT won't let me download their Defender program.// I have a computer that I had "custom made" so I dont have the easy area to click on saying to go back to the basics again like my "factory made computer"did. Where do I go (steps please)? or any other suggestions re spys.thanx