hello,
i had the same problem but after reinstalling and downloading everything i found a simple solution to this problem.
simply doubleclick on the biggest file in the backup folder, for me it was Counter-Strike_disk1_0.sid than choose to connect the file with steam by choosing the steam.exe via browse-button, then click Ok.
I don't know if anyone is still following this but I have just had this problem myself and the way that I got around it was to get my mate to back one of his games up and use his exe file. I have uploaded the file, unzip it and place it in the directory where the sid and sim files are (if they are on cd copy them to pc) and run the exe. It worked for me so hopefully it should work for everyone.
simple fix. http://support.steampowered.com/cgi-...duser/home.php
that will take you to the steam support page, when you get there do a search for "backup restore" it should be pretty easy to find. basically you download the backup.exe file and copy it to the backup folder. worked for me