Serial Number InDesign 7.5 doesn't work anymore

I bought Adobe InDesign in October 2011 and had since then a serial. I bought it online as download. Now I had to buy a new computer, so I also had to install InDesign again, but now it doesn't accept my serial anymore.

I just found CreativeCloud to download InDesign, but the serial is for the version 7.5

Thanks

Silke