Windows restarts on loading screen (safe mode accesible)

hi everyone

well I am going to talk about this problem from the beginning
my laptop was fine running on vista OS and when I heared about windows 7
I installed it and that went fine too
4 months later the laptop suddenly restarts at any time (browsing - playing games .. etc)
I took it to a technical and he formatted it to windows XP then when I opened the laptop it restarted on loading screen (where the logo is displayed)
I told the technical and he said that I should go to safe mode and restart from there I tried this and it worked
a few weeks later and this method stopped working
now I must go to safe mode and restart and go there again and restart ... etc now it is luck which opens it cause it works sometimes and sometimes not
yesterday i re-installed windows 7 on another drive (not C:/) and to complete installation I must restart the computer
now I must choose an operation system on startup so when i choose windows 7 it restarts on loading and the same on XP but I can acces safe mode in XP

My Laptop is toshiba satellite A300 - 4GB Ram - ATI Radeon Graphic card 1GB - 400 GB hdd

thanks for any help
for any information needed I am here

I took my laptop to another technical and he told me that the problem is between the CPU and the fan.
anyone knows how much is this right ?

If you open up the BIOS, you should be able to read the CPU temperature. Temperatures over 80 C could be an indication of overheating.