1.5 Gb of RAM... phones have more RAM these days:)!
Just try to install it, that's the easiest way to find out. Just don't open more than one image (tab) at once, and don't expect to process 36MP images..
The (very soon) upcoming 4.1 version will have lighter memory requirements.
Hmmm . . . my first computer (BBC model B) had 16K RAM, my first Mac 256K, . . .
Actually I've never opened more than one tab and my images rarely exceed 10MB, so I'll wait for 4.1 and give it a shot, especially if it will open early Sigma X3F files
XP Pro 32-bit will be OK then?