Today I managed to migrate my legacy Debian Linux server to a VMWare guest running on my temporary ESXi server without any problem. The downgrade from grub2 to grub (see Downgrading grub2 to grub legacy on Debian) apparently did the trick and after a few hours the migration complete successfully.
I must say I am pretty impressed by the functionality offered by VMWare vCenter Converter (Standaline). Not only does it allow one to migrate physical and virtual machines, when converting a physical machine it also gives you full control over the partitions created.
Tomorrow I will try to get VMWare ESXi running on my Dell PowerEdge 2850 server (apparently that old model still is supported by ESXi 4.1)…