^ What Jeevs said basically but I would also add in case it doesn't solve your problem to check the virtual memory. Don't panic!
I am going to guide you step by step ...
1- Right-Click on My Computer which should be either on your desktop or in the Start menu. Click on Properties.
2- Click on the Advanced tab, then on Settings in the Performance section (top section)
3- On the next screen, you will have 3 tabs (Visual Effects, Advanced, Data Exec bla bla). Click on Advanced.
4- In the Virtual Memory section click on Change.
5- Make sure "Custom Size" is selected. In both Initial Size and Maximum Size enter 1.5 times the amount of RAM (memory) you have. If you're unsure about the amount of RAM you have, right-click on My Computer (step 1) and on the first screen you get (General Tab), in the Computer section on the bottom, you will find information such as CPU speed, Operating System version and the amount of RAM you have (256,512, 1 Gb...)
Once you update these 2 values, just click on OK.
6- Restart your system.
Hope that helped! Let us know if this fixes your problem!