Thanks Vog and TreeBear for your swift replies... I will try the password first because it seems much simpler... It is only to stop prying eyes for the next couple of weeks whilst we are on holiday. Thanks once again.
If you want to lock the whole computer you could set a BIOS and Windows password, which will stop anyone using the machine altogether. However if the computer needs to be used by someone else for business while you're away, then just password protecting your files should be enough.