Strange System Hang

Out of the blue, my laptop will become completely unresponsive. Both my bt mouse and keyboard die, so there's no Ctrl-Alt-Del, even if USB mice and keyboard are plugged in. Also, the power button does not effect a shutdown when pressed. You have to unplug the power cord and remove the battery to reset it.

Microsoft Security Essentials is installed and up to date. The system doesn't slow down before a freeze, it just spontaneously and completely stops. I have run "sfc /scannow" but the log file gives me an access denied message when I try to open it. Might the RAM be loose?

Dell Inspiron 1545
Windows 7 Home Premium x64
Intel T6600
4GB DDR2
320GB Hard Disk
Intel Graphics
Dell Bluetooth 365 (self-installed upgrade over no BT module)
Intel 6200 a/b/g/n (self-installed upgrade over Dell 1397 b/g)

 

Does the freeze produce a blue or black screen or does it just freeze the monitor image?

Have you made any recent changes just before the problem started, new software or hardware, etc.

Click on Start and type event in the search box, Event Viewer will appear in the list above, click on it and the viewer will open, give it a moment to fully load and have a search in the logs for any events that occured around the time of the last freeze.

This problem can be caused by a number of things but first try testing your memory. I suspect you have atleast two memory modules so try running the PC with only one installed and then swap them around to see if you continue to get the freees with each module.

Then follow this to download diagnostics to test your hard drive: