I know with the oem version i can't install it on another computer and if i switch the motherboard it won't work anymore and i'll have to buy another. I want to know if the ssd that im going to install it on gets corrupted can i use the same disc to install it again or will i have to go buy it again?
Oem version can be reinstalled as many times as you want as long as you are using the same MOBO ( OR a replacement MOBO if the original dies under warranty and requires replacement) so Yes you'll be fine if the SSD goes bad - you can replace any parts except the MOBO and reactivate the OEM license and can even replace the MOBO (though doing that requires calling MS and activating manually but they will provide you a new activation if the MOBO fails and requires replacement.)
[Update: As a consumer, you can buy an OEM System Builder copy of Windows from countless online shopping outlets. Technically, you're not supposed to use those copies unless you're building a PC for resale to a third party. But Microsoft's own employees and retail partners, and even its own "decision engine," Bing, aren't so clear on the rules. For a detailed discussion, see Is it OK to use OEM Windows on your own PC? Even Microsoft's not sure.]"
Guess that's why we get some leeway when activating systems which have undergone major changes...but have no 'come-back' if it's refused...