Reinstall OS with no CD drive

Hi all, first post so bear with me!

I'm having issues with my Dell XPS 18 tablet and I need to reset to factory, that's pretty straight forward for me. The re-installation of Windows is not.

I have the original CD but the tablet has no CD drive. I don't have the money (or time or use etc) to warrant buying an external CD drive and I don't have a large enough USB flash drive, (it's only 512mb). I do have a 500gb Ext.HDD.

Can I do it using this? If so, how? I saw one video stating that I had to create an ISO file or something, that bit has gone straight over me.

It's Windows 8 64bit if that changes anything.

Also, the tablet has stopped working without a power connection and says "no battery is detected". Anything I can do?

Any help would be appreciated!

Thanks,
Pete