Windows 7 have inbuilt diagnostic tool to check bad, or corrupted RAM. To use this
Control Panel => Syatem and security => Administrative Tools
And run Windows Memory Diagnostics
This will open a window like below,
Choose the option you like. After reboot you can.
Advanced options for running the Memory Diagnostics Tool
When the Memory Diagnostics Tool starts, press F1.
You can adjust the following settings:
Test mix. Choose what type of test you want to run: Basic, Standard, or Extended. The choices are described in the tool.
Cache. Choose the cache setting you want for each test: Default, On, or Off.
Pass count. Type the number of times you want to repeat the test.
Press F10 to start the test.