Put the contents of a VDI in a VHD

To run an old program I need Windows 98. But I noticed that my virtual machine (Windows 98SE) had no sound card! After much research I understood that there was no hope of having a virtual sound card for Win98 with VBox and I read that someone had, in his regret, pass under Virtual PC for Win98 with sound. NOTE: my host system is Windows XP (Win Vista sometimes, I often ride my files). Windows 98 system is my guest.

But to avoid having to reinstall everything, I would like to remove the data from my hard drive for virtual VDI place in the VHD (format of virtual hard disks for MS Virtual PC).

Do you see any way to do this?

Thank you in advance for your answers

1) You install Windows XP on VBox and under Virtual PC.
2) Since your windows XP on Vbox you mount the virtual disk win 98 and you do a ghost of your win98.
3) You transfer the image of your Virtual PC to ghost over the network (if you arrives not mount the network between two virtual machines or if you do not have enough RAM for the turn 2 virtual machines same time, then transfer it to your "real PC" in the meantime.)
4) You begin pre-installing win 98 in Virtual PC (to configure the MBR and data that are not in the ghost)
5) You mount the disk of your pre-installation so that it can be seen by your Windows XP under Virtual PC.
6) You crush your pre-installation by reinstalling your ghost above.
7) Your Windows 98 should be able to run independently under Virtual PC (hoping that the same processor that is emulated in both machines)

See this link from the official site : http://forums.virtualbox.org/viewtopic.php?t=9327

Hope this help you .

Thank you very much for your answer

I managed to transfer this VBox on VPC