Windows Vista Slow Running and Programs Not Responding

I had HP custom build a PC for me a little over a year ago, It is a M9200t with Intel Core 2 Quad Q9450 @ 2.66 GHZ, 8 GB of memory and 500GB Data Security HDs running Vista Ultimate. After about 2 it over 10 minutes to startup and and ran slow after startup with all the programs not responding. I had all up to date virus and spyware protection using Kaspersky and Webroot. I tried restarting and that wouldnt help with the problem taking about 20 minutes to do a complete restart, so I decided to do a complete restore which didnt help. Letting it run slow it would get to the point where it wouldnt run at all so I shut it down by holding the power button and after doing that it ran fine. From that point on about every one or two weeks it does the same thing leaving me with nothing to do but shut down by the power button. I have the PC performance gadget on the sidebar and when acting this way both the CPU and Memory are at a normal percent. I have tried turning unneeded programs off, and tried different virus protection software like Kaspersky Bitdefender ESET and Norton. It also doesnt matter if it is startup or coming out of sleep and hibernation they it just seems to happen starting up from all. Today it did it again after work starting up from hibernate but this morning it ran fine. I did a complete restore again about a week ago with just the basic programs on it now. I also used a registry repair program but that just messed of some programs and I had to do a restore point. Is there anything I should try to do? I consider myself to be pretty good with computers and can fix most problems but cant figure out anything on this and have researched with no luck of finding a solution. For a while I thought it had something to do with my Vista and Windows Auto Update since it seemed to do it shortly before updates were installed so I turned it off and updated myself but it didnt fix it. I used to just happen every Friday or other Friday but does it whenever it wants now. I have also wondered if it has anything to do with the Intel Matrix Data Security but am not sure.