I have a HP EliteBook 8560p with 4GB ram and a 2,5Ghz i5-2450M processor running windows 7.
My question is: will I be able to run the WP8 SDK on a virtual mashine running W8 that i give 3GB ram to or will it be to slow? The system requirements for the SDK says 4GB minimum. Unfortunately this is my schoolcomputer so I am not allowed to install W8 as the operating system, that's why I want to use a virtual machine.
Adding to MDumitru answer, you should install virtual box not VMware. Windows Phone 8 SDK requires hardware Hyper-V support1. You can follow this article while installing VMware and WP8 sdk inside it.