How can I format my pc I lost the administrator password.?

Answer 1

Just insert your xp cd and follow the prompts. Just as a heads up, you will lose whatever data is on the machine.
Total re-install time including printer and ad-on software should be less than an hour.

Answer 2

But the Windows CD in the CD drive
Boot the PC from the CD
It will start the Windows set up
After you press the F8 to agree, it will ask you about formatting and creating partitions
Select that you want to format the drive (usually with NTFS)
Once the format is complete, you may either turn off the PC or let it finish installing Windows