To check the Windows version, amount of memory (RAM) and processor speed
Go to Control Panel, System, or right-click Computer/My Computer on the Start Menu or Desktop, then click Properties:
With Windows XP, you will see the box below, showing details of the Windows Version and the processor speed/amount of memory. The system shown below is 32-bit; a 64-bit version would say "x64 Edition".
With Windows Vista or Windows 7, you will see this:
To check whether you have a single, dual or quad-core processor
Right-click Computer/My Computer and then click Manage. In the Computer Management window, click Device Manager in the left-hand pane. Then, in the right-hand pane, click the plus sign or arrow just to the left of Processors. You then just count the number of processors that appear! The picture below shows a dual-core processor (it might actually be two completely separate processors, but for our purposes, there's no difference).