I've been told I can't use my work laptop for personal use. How do set up my laptop to boot to an external HD rather than the on board HD.

That's still personal use, but if the laptop supports it there should be an option in the BIOS for boot device order or selection.

I know what u mean with personal use. Just change the boot priority so the first boot device is "USB HDD" in the bios setup and en cd drive and then first hdd then when you beet the laptop up with out a external hard drive it will start up normaly. Let me know if you got it

Thanks for that, how do I access the bios and how do I load the OS onto an extn HD or can I buy an extn HD with an OS on

It's very easy actually you just plug in the external hard driveve and install windows like normaly but you should be very carfull when installing so you don't get confused with the hard drives and install it on the computers hard drive instead of the external one , ilke if you buy an 250gb external hard drive make sure you install it on that one and not the outher one. And if you got it then just change the bois settings so the computer has a boot order of 1.cd drive 2. usb hdd 3.hdd or hdd0
If you not sure let me know and ill go into more detail just give me the specs of the laptop as well ex. Name etc