To directly answer your question, yes, if you buy an OEM version of the same edition of Windows 7 (you cannot move from Home to Pro or vice versa) then you will be able to re-install Windows. Dell are pretty good at offering all the drivers for their laptops on their website too.
![Windows Windows](http://getintopc.com/wp-content/uploads/2015/09/Dell-Genuine-Windows-7-Professional-OEM-DVD-ISO-Direct-Link-Download.jpg)
However, you don't have to buy an OEM version of Windows 7 from Dell. If you can get hold of the retail version of the same edition of Windows 7 (and there are multiple ways to do this) then you can edit a file on the disk to turn it into an OEM version - which will then happily install and register using the product key attached to your laptop. Full instructions to do this can be found at.
So, now if you own a Dell laptop, and want to reinstall Windows 7 Home Premium then you need the Windows 7 installation disc. If you don’t have the disc, then you need to download the Windows 7 Home Premium ISO. So, here is how to download Dell Genuine Windows 7 Home Premium 64 bit ISO. I've got a Dell Latitude E6410 Laptop with a Windows 7 Professional OS installed on it which needs a fresh win install on it. I would like to download a win ISO since I haven't got the windows cd but I can't download it from the Microsoft website because is a OEM version I think.