I have a prs-505 and a Windows 7 pc. I have an older version of the Sony software: 2.5 which works perfectly except that it won't load the Sony store, which doesn't bother me as I don't buy their books.
I had to do an extensive search to find a site which still had the software. Newer versions could see my reader, but I didn't like how they worked. If you want, I'll have a mooch around and see if the 2.5 version is still available anywhere.
But it sounds to me like you're giving up easily and maybe really want to buy another reader. If so, go ahead.