To be honest with you, I have also had a Windows server before and never got the Unrar/rar addon working on Windows.
I have since moved to a Ubuntu server with NX virtualization (pretty much like mstsc, except for Unix systems) and never going back.
If you wish to know about it, contact me, I can hook you up with real cheap prices and amazing speeds (I really mean amazing, I am achieving 9MB/s on RapidShare as we speak now). I am not the owner of those seedboxes, but the guys I have got it from they provide you with amazing personal customer service and can be reached on IRC.
There is no commission or percentage that is sent my way, I am just not wanting this service to become oversold, nor do the original owners.