I don't want to make any assumptions but I see in your pic what appears to be 4 drives in the server marked as healthy and 1 missing drive which maybe the result of your physically removing the drive and then replacing the drive to add additional capacity and then you selected the drive for removal. Am I correct in this and if not please do correct me.
As for the removal process its even painfully long when it goes well. Unfortunately you have to allow WHS to remove the drive. I will also add that just because WHS reports the drives as being healthy that it may not actually be the case. WHS looks at the file system and on occasion does run a CHKDSK to help it to determine the health of the drive but this applies to the file system so WHS is only telling you half the story because its not looking at the physical condition of each drive. There is software that can be installed on WHS that can read the physical health of the hard drives one such ADD-IN is HomeServerSMART Classic which is free.
http://www.dojonorthsoftware.net/Downloads.htmlThe one thing about WHSv1 is its extremely sensitive to drive conditions and after all its all about the drives in any server but if you happen to have another drive acting up it could be the cause of your problem.
The other thing worth mentioning is if you happen to have the newer Advanced Format Drives or AF Drives and there is a ton of information on the site about those. Some are plug and play others need jumpers others need alignment and what you need to do to run them in a Legacy OS like WHSv1 varies with each manufacturer and sometimes the model which is why I do not mention specifics about them and for the most part do not make recommendations on which drives you should use in your server. I still run WHSv1 but if I need a drive I can move an older drive from one of my older servers and install it in a WHSv1 server so for me I try to avoid the AF Drives although I have tried some drives which are 512e meaning they emulate the 512b sector size.
I am surprised no one has chimed in here. I did see your post the day you posted it but I was busy with a retro project I have been working on and thought someone would of assisted you but you have my attention so lets see if we can sort out this issue if it still exists.