We've finally reached the point where it's cost effective to supply a PC with more memory than 32-bit Windows can handle, and I personally suspect that Windows 7 will be the last Microsoft OS to be offered in a 32-bit version. If you find yourself performing tasks that push your computer to use more than 3GB of memory, you should be considering . People who use their computers for office apps and Web surfing don't really come close to exceeding the limits of a 32-bit OS. But if you find yourself running virtual machines, editing HD videos, and manipulating 12MP raw images, it's probably time to switch to a 64-bit OS. The Windows 7 Upgrade Advisor can tell you if your CPU is ready for it.

Does it make sense to sink money into my old computer?

Purchasing an upgrade to Windows 7 Professional will set you back a solid $200, while Home Premium will run you $120. That's a serious chunk of change that could otherwise be applied to a shiny new PC. Considering that a new laptop can be had for under $330 and $800 will buy you something pretty sweet, it's easy to see that $120 to $200 as a discount on a new piece of hardware which already comes with the edition of Windows 7 that you want.

There's also a bunch of newer features that a computer that's more than couple of years old may not have, such as HDMI, Blu-Ray, eSata, 802.11n, and LED backlighting.

If you've got a kid who can use your old computer for school, or if you really find yourself wishing you had an extra machine in the office, it might be best just to leave the old computer as-is and treat yourself to the latest technology. Besides, you deserve it, and our economy desperately needs your contribution.