PSE 7. Serial key does not work anymore.

I needed to reinstall my whole system. I've downloaded Photoshop Elements 7 from the official Adobe page (German version). When I type in my Serial key (It's from 2009) the key does not work and I get this message: "Die eingegebene Seriennummer is ungültig"(The entered serial number is invalid).

I asked the live support and got the information that the activation server does not work anymore because the version is too old... I got the suggestion to ask in the forums or buy an upgrade, but I can't buy an upgrade because I've absolute no money right now and I won't have money to buy it in the next two month.

What can I do to activate my product? I really need a working version of PSE for my work right now...

Greets,

Lukas