I successful converted a machine from physical to virtual. The physical machine has one hard disk with two partitions.
I made a fixed vhd of 300gb and I see 2 partition, one of the system and the other one is unallocated. I don't want to create a new partition, I want only one with the full space.
I tried with partition magic but it says that there aren't any parittion to merge.
This is what I see in disk management
What you want to do is expand the existing partition to consume the entire disk. From Windows Server 2008 onwards, you could expand the system partition online, so we need to know which OS your VM is running. If it is running Windows 2003 R2 and older, your options are to either use a 3rd party tool or booting the VM using WinPE and expanding the partition offline using diskpart from within WinPE. The latter is quite easy to do.
The process is described in this document: How to extend a data volume in Windows Server 2003, in Windows XP, in Windows 2000, and in Windows Server 2008