I've had my computer for about 3 years now. it's a Dell XPS M1530. nice laptop, Powerful for when I bought it. 2.5 GH dual core, 4 GB ram, nvidia GeForce 8600m GT. it cam with a Vista 32 bit os
About a year ago I upgraded to Windows 7 32 bit
here is my discovery, my computer is 64 bit capable. about a year after I bought my laptop they started selling the exact same modal with a 64 bit OS! no difference in hardware the motherboard and processor ect are 64 bit capable. so just to day I formatted my HD and installed the 64 bit version of 7. (don't worry I saved all my files)
I just gained half a gig of ram by upgrading and it seems to be running faster too. I'm running an average of 5-8% less CPU under normal operation.
WHY DID I NOT DO THIS SOONER!
To answer your question bluntly, you obviously didn't know. :3 Its awesome to hear your computers running better.
I just stumbled across this, and I thought of this post.
http://www.igorware.com/64bit-checker/download
Its a tool that will tell you if your processor is 64-bit capable or not. If you were thinking about upgrading, it could save you some time looking it up.