[SOLVED] My PC is restarting after 2 minutes

[internetisbest]

Hello, sorry for my English. I'm from Turkey. I bought a new Fan for My Core 2 Duo E6600 and I overclock 2.4 GHz to 2.7 GHz from BIOS. And I restart my computer for check Windows. Windows is normally opening, but after 2 minutes, when I click anywhere, PC is freeze for 1 second and restart. I reset the BIOS for default settings. Then, I open the computer and I get a blue screen 0x000000A5 error. I restarted the computer without doing anything because this error had nothing to do with the problem because I had corrected the ACPI setting. Then, I choose 'Start Windows normally' and PC shows 'Windows is loading files' screen. I wait for end this, But the computer started again after finishing this process. I again clicked 'Start Windows Normally' and system will open. But, PC is again freezing for 1 second and restarting. I check the temperature on BIOS, CPU temperature is 25-30 celcius.
And that's how it goes on. How can I fix that? I cant find solution on Turkish Forums.

 

[Lutfij]

This is a thread of troubleshooting nature, please pass on your full system's specs like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:

After you reset the BIOS, did you check and see if your Storage controller was set to AHCI(in case if it's reverted to IDE).

 

[internetisbest]

My PC specs is:
Core 2 duo E6600
2 GB (1+1) 667 MHz Kingston DDR2
MSI MS-7255 VER 2.1
PSU: Everest 400W (I don't know model)
GPU: ATi HD 4550
OS: Windows 7 32 bits
HDD: 40 GB old HDD but using only for Windows, I using 320 GB external HDD for games.
Chassis: I don't know, an old Casper chassis.

 

[internetisbest]

My HDD is connecting to IDE cable.