A Dell Studio 1555 is having strange power problems.

Dear readers,

I'm having big problems with a Dell Studio 1555.

It falls out constantly. When i want to start it with the power button it won't work.

1. When I put out the battery and put it back in, immidiately the power is on. I see the POST and press on F12 for the boot option. Then the screen turns black. But when I switch between screens with the F2 button it comes back on the laptop. I start the Windows 7 DVD. The process starts until i see the green bar with 'Microsoft Corporation' below it. Then the power shuts off.
2. Same happens if I start it from the harddisk.

What have I done so far:

• I checked the harddisk for errors. Nothing found.
• I checked the harddisk for virusses and malware. Nothing found.
• I put out the CMOS battery for 10 minutes. Result is the same as discribed in point 1 en 2.
• I put out the battery (accu), pushed the powerbutton for 30 secs without the adapter. Put it on the adapter without the battery and pushed the powerbotton. Same happens as in 1 and 2.

Does anyone know what the problem is or the better, what the resolution is? Please help because I have no clue.

With regards,

Marco van Groos