Are both operating systems the same, and are the files in the same locations, same user-id, passwords etc for system and for Firefox.

Were all applications closed when you copied, and since the question is for Firefox had you verified in the Windows Task Manager that Firefox was down before doing the Link.

On the new system try bringing it up in Safe Mode

• http://kb.mozillazine.org/Safe_Mode

The operating systems are not the same - one is Vista one is Windows 7. I believe files are in the same locations, user IDs are not the same. Ohh and the transfer has never been finished cause one laptop got into hibernation mode and the connection got cut off. and I had used firefox before I started the transfer, it worked fine. actually I used it during the transfer for a moment. I am gonna try Safe Mode when I get home. Thank you:)

I have tried Safe Mode, dint work:/ I uninstalled Firefox and installed it again and now I cannot even open it... Internet explorer works without problems. now I cannot even open safe mode either...

I transferred all of my profiles from Vista to Windows 7 in Jan or Mar of 2010, no problem same files and everything. I used external HD for most of it, and some` USB thumb drives.

I expect that you might want to take a look here http://dmcritchie.mvps.org/windows-7/win7.htm#list at item #10, hidden files read only files, system files.

Laptop power settings look for the battery/plug icon on the windows 7 task bar , click on more power options change the plan in use to never put laptop to sleep when plugged in. If you have something copying files you might want to make sure both computers are plugged into a UPS.