How can i put a password on a Folder, in windows xp?..

You could change the permissions for the folder you want to protect

Right click on the folder to be protected, select 'sharing and security' click the security tab and change the permissions so only you can access the folder. Obviously you'll need a password protected administrator account only you can use, and a restricted account(s) for everyone else for this to work.

Dave

You can also

1. Right-click->Send To->Compressed (zipped) Folder
2. Double click on the zip foler just created
3. Menu->File->Add a password