I have been having a very strange problem. I upgraded an old Pentium 4 3000mhz singe core computer some one gave me. One upgrade was a 1 terabyte sata drive. I immediately installed an antivirus after the operating system. After a few months of everything working well Everything started to slow down. websites did not load right and The antivirus would not update and when i used You Tube for awhile I got the blue screen of death. I did a restore and everything worked better for a time and this cycle went on. Eventually i had to do a fresh install but it would not work. I decided the hard drive was bad. Incidentally I have tried many antivirus non of which helped. I bought a brand new "solid state 60 gig drive and a 500gig regular drive. The regular drive overheated and i returned it to the store. they gave me a replacement but am afraid to try it. Strangely the solid state hard drive works fine. have not had a problem with it.