I had installed the CS4 trial and it had expired. I bought the CS4 program (with a student discount). I tried to install it but it would not install. I kept getting error messages informing me that the program had expired. I had a legit serial number and was frustrated enough to call Adobe tech support. The tech support guy had me go to (I have Windows 7) C then Program Files (x86) then to the Adobe file. Now here is where I am losing my memory just a touch. Somewhere in there he had me locate the file called cache.db. He had me remove it to my desktop. One note... I had before the call reinstalled the CS4 program. Of course I could not do anything with it. I continued to get that dreadful error message. Anyway, after removing the cache.db file to the desktop, I was able to open the program and put in my serial number and now all is fine. I hope this is helpful to someone.... Happy Holidays!!

I forgot to mention... The Adobe tech support person said I could now just delete the cache.db file from my desktop straight to the recycle bin.

thanks for that info TEXAS-Lady. im glad u got it solved

You're very welcome. I just hope this tidbit of info helps someone else!!