Computer Certificates from win2003

Hello! We have a Win 2003 Server in our Lan witch is distributing Computer Certificates. On the pcs this is working fine, however we are not able to download the on the mac.. Here we are only able to download user certificates. We are logging on on the server via web xx.xxx.xxx.xx/certsrv. We get prompted for password and access is granted. Anyone know how to download / request computer certificates from a local server? I have tried the Certificate Assistant, but this utillity will only connect via mail. Mail is not enableb on the win server. I would really appreciate any input on this! Thanks! Thomas