Let me start off by mentioning I am really really new to this whole VMWare ESX/vSphere thing, so apologies if this is a FAQ or asked a million times before using better wording. Also, please correct me if I'm using the wrong terms all over the place.

We just got this brand new VMWare EXS server, and we started importing virtual machines from around the office. Some of them were originally based on VMWare, others are converted from MS Virtual Server.

One of these machines needs a bigger disk, but in the vSphere Client the disk size spinedit is disabled. Disk type is thick. However, for other machines, with the same disk type, the spinedit is enabled and I can happily resize their disks.

So here is the question: why can't I resize this disk in particular?

All machines are freshly converted, so I assume there are no snapshots yet, which I read would stop a resize from happening (again, correct me if I'm wrong).