I am running Whitebox linux and we are in the process of deploying over a hundred new workstations in one building. Under normal conditiions, we would have enough ip addresses. Because, we have the ip address for the old system and the new machine is asking for a new one, we are running out of IP addresses. From what I have read in the documentation that I can find, If I delete an address in the dhcpd.leases file and restart dhcpd I should have that address available.

That sounds too easy. I will also frecquently see what appears to be multiple entries for the same machine int the dhcpd.leases file, so I have a feeling that that is not going to work.

well just explain to me how come that you have run out of IP addresses.
It just seems ridiculous. For example if you have run out from 192.168.0.1 -192.168.0.255 you can still choose another class IP (like 192.168.1.1-192.168.1.255)

I have a pool from 192.168.110.175 to 192.168.110.254. Normally this would not be a problem but we have been in the process of deploying new workstations. The problem we had last week was the old PC were on dhcp and the new PCs were looking for new addresses. We also ran into a problem and were forced to re-image about half of them. We are using Novell's Zenworks and the image process also requests a separate address. We have to deploy about 45 workstations in that building on Next Wednesday and even it we only have to reimage 20%, its going to be a problem.

Can you change the lease expiration until you are done?
I ran into a similar problem when imaging a bunch of boxes and the lease duration was set to never expire. I set it to one hour to give enough time to make the images.

Can I set it just for that scope or network?

There is a good example of what you may want in
man dhcpd.conf under the section called ADDRESS POOLS.