Can't sign in/launch Element 12 on a PC running Window XP

Hi,

I purchased a computer and it comes with Adobe Photoshop Element (And Premiere) 12.

I installed the program successfully on a Window XP, and during the installation, it asked for the series number which I have entered.

After installation succeeded, I reboot the machine and then try to launch the program by clicking in the shortcut.

The program started with a screen showing

"Sign in Required:

You must sign in with adobe ID and registering it within 7 days otherwise you won't be able to use element 12..."

And at the bottom right, there is the "Sign in" button.

After I hit the "Sign in" button, however, a spinning wheel comes up and after a couple of minutes, it gave up saying

"either no Internet Service or the  clock itime on my computer is wrong " although neither is true.

Please help.

P.S. ,  installed the software six days ago on another PC running Window & and it worked. I did register the software - is it because the software can only be installed/used on ONE computer ? Do I need to uninstall it from the other Window 7 computer for the software to work on this Window XP computer?

Thanks.