need help in securing VMLITE please

Hi:
Yesterday for the first time I installed VMLITE with win xp mode on my win 7 ultimate pc and was wondering what tweaks do I need to do to make the VMLITE secure as not to let things to go from VM to my host pc. Things like infections etc. The reason is that I want to start testing anti-malwares using malwares and do not want any infection to cross into my host pc. Any hardening or tweaking idea is welcomed. This is what I have done. I have made the C and D driver read-only and have turned off "bidirectional: option in the setting. I also have a USB options activate (without any protection). SO can anyone tell me more hardening securing procedures to do so to have a real isolated virtual machine before I test malware in it. Thanks in advance for your help.