Question : Key combination split desktop into 4

I accidentally hit a key combination or something on my keyboard, and my screen split up into 4 boxes not sure how to explain it, but I'm wondering what the key combination is for this and how to set it back?

Am running Windows XP Pro on a Dell OptiPlex 960 with ATI Radeon HD 3400 Series video card.

Answer : Key combination split desktop into 4

You should be able to set it back by going into the graphics card utility which on your case is the ATI control panel and deselecting the option.