|Your laptop specs from Sony show that it is a 64bit processor so you can install 32bit or 64bit. However, Vista was rather annoying in that whilst many of the retail copies would use the same key for both 32bit and 64bit version, the oem versions of Vista were sometimes limited to just what the supplier wanted to install. As your system specs say it can only take a maximum of 2Gb of RAM I would suspect that the version you need is the 32bit.|
As you've discovered, Vista disks are very rare and you may have to rely on asking around amongst friends to see if anyone has a (preferably Sony) oem disk that you can try. Don't use the 'activate when online' option as you'll almost certainly have to go through the telephone activation route once you've downloaded and installed the manufacturer's drivers, but as it's a branded machine that should work ok.
"I've always been mad, I know I've been mad, like the most of us..." Pink Floyd