Your System event log contains

<b>        Event id: 49
        Source: FTDISK
        Description: Configuring the Page file for crash dump failed. Make sure there is a page file on the boot
        partition and that is large enough to contain all physical memory.</b>
I suspect you just added RAM and your computer was configured to create a Crash dump, Memory.dmp.

The pagefile.sys needs to be increases to hold the Memory.dmp file:

1. Right-click My Computer and press Properties.

2. Select the Advanced tab.

3. Press Performance Options.

4. Press the Change button in the Virtual Memory area.

5. Set the initial size (MB) and Maximum size (MB) to the 1.5 times the amount of RAM in your system.

6. Press OK / OK / OK and restart your computer.

If you don't want a Memory.dmp file, you should also:

1. Right-click My Computer and press Properties.

2. Select the Advanced tab.

3. Press Startup and Recovery.

4. Select None under Write debugging information.

5. Press OK / OK and restart your computer.