[Howto] find all your 100+ vbox VMs back after reinstall OS

[nobook]

We suppose our PC stored 100+ virtual machines stored at D:\VMs, and we need format C:\ reinstall OS, whats the best and fast way find all our VMs back after reinstall OS and Virtualbox?

1. Export to ova and import back after reinstall?
No, it take long time and lost all snapshots of VMs.

2. Register every VMs (100+) after reinstall?
No, it take long time and you may not get some VMs back because they created by vbox v3.x and vbox v2.x, with diffrent .xml and .vdi paths. vbox 4.x can not register disk media .vdi anymore.

3. Recreate all VMs and add .vdi back and settings back manually?
No, there are 100+ VMs!

4. Follow some clone posts...
Slow.

Finally, I find the best and fast solution.

Backup C:\Users\{username}\.VirtualBox\VirtualBox.xml
and copy it back after reinstall OS and VirtualBox.
Run VirtualBox and you will find your 100+ VMs come back, all snapshots, everything totally like before.