If you have a OEM recovery partition, then you should be able to press something like F10 or F11 every second during boot until you get to your OEM recovery manager screen. From there you should be able to select the restore to a factory default installation option.
If you can post back the brand and model number of your computer, I may be able to post back a link to the OEM's website with more detailed instructions for your particular OEM brand.
You will have to start all over again from scratch and lose all downloads and documents and personal modifications you have done. And then possibly, you might do again whatever it is that you think so messed you up to necessitate factory setting restoration. Huge step!!!