Create the VM, start it once, then power off and edit the .vmx file (you will need shell access) and add at the end
bios440.filename = "dellbios23.rom"
For 2012 R2, Install the VM using this key
2012 R2 STD 2FND4-FCR66-RK9Q3-F82H3-4GB43
Once the machine is booted up, open a command prompt as Administrator and run "slmgr -ilc DELL.XRM-MS"
For Windows 7 and Windows 2008 R2, apply the key with
slmgr -IPK XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
using these keys:
W7 PRO 32KD2-K9CTF-M3DJT-4J3WC-733WD
2008 R2 STD D7TCH-6P8JP-KRG4P-VJKYY-P9GFF
2008 R2 ENT BKCJJ-J6G9Y-4P7YF-8D4J7-7TCWD