If by 'talking' you mean networking. Macs and PCs will happily exist on a network together. You can share files and printers. What is it exactly you want to do?
As far as someone giving you serial numbers to commercial software. You're out of luck. Legalities aside it's against the forum rules.
What OS and Mac are you using? OSX will network just fine with Windows. If you mean the old Pre OSX OS9 and before, then you would need something like Dave.