As for procuring a Windows 8.1 Reinstallation DVD/USB from Dell; if in the US or CA you can try the online media request form: www.dell.com/recoverymedia For non-US or CA regions Dell haven't made an online request form unfortunately and you have to call Dell Technical Support.
My friend gave me her Inspiron 3135 because it needed a new hard drive she also asked me to put Windows 7 on it because she doens't like 8. I did all that and once I got windows 7 working, it was time to get the drivers working because almost nothing worked. I loaded all the necessary drivers onto a USB stick and started trying to load them on to the netbook. Each one gave me the same error, something along the lines of "This software cannot be installed on this platform". I suspect this is because I am trying to install drivers meant for Windows 8 on Windows 7. Does anyone know where I can get drivers for this machine that will work on Windows 7? If not, how can I get a Windows 8 recovery disc from dell because the recovery partition was on the old HD and it's toast. (can't wait for the autopsy) 
Windows 7 Drivers for Inspiron 3135