Could be a long list of things that might be the cause of this. The most critical is aging hardware of which, I'm at a loss of helping with.
Couple of things we can try
Download blue screen viewer from the link below and install and run it to read the dump files created by windows.
http://www.nirsoft.net/utils/blue_screen_view.html
Double click on BlueScreenView.exe file to run the program.
When scanning is done, go Edit>Select All.
Go File>Save Selected Items, and save the report as BSOD.txt.
Open BSOD.txt in Notepad, copy all content, and paste it into your next reply.
~~~~~~~~~~~~~~~~~
Please download the Event Viewer Tool by Vino Rosso
http://images.malwareremoval.com/vino/VEW.exe
and save it to your Desktop:
2. Double-click VEW.exe
3. Under 'Select log to query', select:
* System
4. Under 'Select type to list', select:
* Error
* Warning
Then use the 'Number of events' as follows:
1. Click the radio button for 'Number of events'
Type 20 in the 1 to 20 box
Then click the Run button.
Notepad will open with the output log.
Please post the Output log in your next reply then repeat but select Application.
These 2 tools may or may not supply us with information but we'll see.