Change the boot order to boot from CD or a memory stick.
Try googling how to access the recovery partition on your laptop. It should be a key sequence you enter at startup. This will allow you to re-install the version of software that it shipped with.
There is no boot order, only just the hard drive and the option to add additional things but I have no idea how to do that. I do think it might have a recovery partition, I had upgraded it to windows 8 pro but I seem to have lost the new key, so that would be a waste of $100 too if it even still works.
Do you know the P/N of your motherboard (or PC if its an OTS box)? If you google it and 'boot order', you can probably find a simple walkthrough to change the settings. Or maybe someone here can help.