How to add a disk to a Windows VM

Hello all,

I ran into something supposedly easy, but it seems I'm missing something:

I added a 50GB IDE hard disk (LVM on iSCSI) to a Windows VM (Server 2008R2) through the Proxmox GUI. The new HD is IDE1, the boot disk is IDE0. I rebooted the Windows VM, but I can't see the new hard disk in Volume Manager.

Does somebody know what I'm doing wrong?

Thank you very much.