Windows not loading?

I am using ME with AVG anti virus, no-adaware and Zone Alarms firewall.
Recently i am having a lot of trouble with windows not loading at start up or locking up part loaded leaving me to switch it all of and either it restarts in safe mode or with the Scan disc check which again locks up sometimes.
Occasionally it will load correctly but as soon as i try to do any thing it locks up.
When eventually i do get it to load after the trouble the PC works fine.
I have done all the updates and scans which also dump my Temporary Internet files and there is an improvement but after a few days it all returns again to not loading.
Any help would be appreciated.