Help me with this one...

I've requested some more experienced members to take a look since I have no clue what to do.

Hello,

I suspect the system is overheating:

Code:

Event[107]:
  Log Name: System
  Source: Microsoft-Windows-Kernel-Power
  Date: 2011-03-27T11:55:17.994
  Event ID: 86
  Task: N/A
  Level: Error
  Opcode: Info
  Keyword: N/A
  User: N/A
  User Name: N/A
  Computer: Marie-PC
  Description: 
The system was shut down due to a critical thermal event.             
Shutdown Time = ?2011?-?03?-?27T15:55:17.994033200Z             
ACPI Thermal Zone = ACPI\ThermalZone\THZN_CRT = 378K

Converted to Celcius, that represents 104.85. When you replaced the hard drive, did you replace all heat sinks and air channels? If not, be sure to do so now. You might also make sure the air vents are not plugged with dust, using a can of compressed air.

Check your temps with Speedfan now, just for reference; post them here.

SpeedFan - Access temperature sensor in your computer

I'm also seeing these errors:

Code:

Event[214]:
  Log Name: System
  Source: atikmdag
  Date: 2011-03-26T10:39:34.826
  Event ID: 43029
  Task: DAL
  Level: Error
  Opcode: N/A
  Keyword: Classic
  User: N/A
  User Name: N/A
  Computer: Marie-PC
  Description: 
Display is not active

I will admit I don't really know what that means, but I do know your ATI drivers are out of date:

Code:

atikmdag.sys Fri Apr 24 06:51:57 2009 (49F199CD)

Install these updated ones: ATI Catalyst

...Summary of the dumps:

Code:

Built by: 7600.16385.amd64fre.win7_rtm.090713-1255
Debug session time: Sun Mar 20 21:25:17.817 2011 (UTC - 4:00)
System Uptime: 0 days 0:00:27.892
Probably caused by : ntkrnlmp.exe ( nt!ExpSystemErrorHandler2+5e1 )
BUGCHECK_STR:  0xc000021a_0
DEFAULT_BUCKET_ID:  VISTA_DRIVER_FAULT
PROCESS_NAME:  smss.exe
FAILURE_BUCKET_ID:  X64_0xc000021a_0_nt!ExpSystemErrorHandler2+5e1
SystemProductName = Satellite L305D
¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨``