how do i add a password so that each time the pc is turned on before it boots up its asks you for a password?

or is there anything else you could recommend to stop unauthorised access to my laptop?

You need to go into the bios and set a password. There are usually two passwords that you can set in the bios, those are setup and boot. Setup password would be asked for when you try to access the bios, the boot password is self-explanatory.

you have two protection options here, you can use them both depending on your operating system.
first - you can enable the password protection on your BIOS, hence everytime the P boots before it even gets to Windows it asks you for a BIOS password.

second - enable a password on your Windows Profile. You see this option depends if you have NT workstations or 95/98/ME workstation.

thank. it windows xp am on. how do i get into bios?

usually F1, F2, F10 or delete to get into the bios. Check with your laptops manual and it should tell you if none of the above work

And the Windows XP password is useless because it is so easy to get around if someone knows what they are doing.

if you have a valuable data on your system there is a software package that would encrypt your HDD in one password.
This is a high protection method.

press delete button on your keyboard after turning on computer and before it boots up.