I'm running windows xp x64 Trial version (120 dasy eval)...
After the eval period if I would like to stay with it I'll have to reinstal everything from scratch from purchased original x64 disk or I'll be able to enter just a serial number or something like that and avoid reinstallation of everything ????
I think you can do it from your current install although it was a long time ago when I did it for Server 2003. Go into the Windows Help and type 'activation'. This will bring up the directions to activate.
If this doesn't work, you should be able to install your installation disk, boot to the Repair option and then click Repair Windows. This will then reinstall Windows and ask for your current product code. You will need to reinstall any Windows Updates as it will roll back your system to a fresh install. Make sure you pick the Repair Windows option and not the install option. The repair will remember your current settings and application installations.