Hi, Chromian,
PCG-7185L is just the chassis number. Based on the specifications of your Sony VAIO VGNNW250F, the unit came with Microsoft® Windows® 7 Home Premium 64-bit. You cannot just install any operating system to your machine. What we recommend is to get a recovery disc and install it to your computer. Visit here order a recovery disc: https://sony.encompass.com/general/Contact-Us.
Regards,
Vincent
If my post answers your question, please mark it as "Accept as Solution"
