My Question is:
If you got UnleashX and a new HD (unformated/w/o partitions), can you use UX to set it up?
EvoX got the configsector disk.bin stuff and MxM also knows howto partition a new HD, but is UX able to do so?

yes just put it on a disc pop it in and follow the instructions

As tweaqr said.

You can also also put the content of C drive in "CDrive" or "CBackup", E on "EDrive" or "EBackup", F and/or G on the same, assuming it will still fit on a single disk.

If the dash, after restoring C, or you don't have C backup at all, can't find "xboxdash.xbe", it will install itself as "xboxdash.xbe". If it's there and "evoxdash.xbe" isn't, it will install itself as "evoxdash.xbe".

Aaaaaaah...
Thats very nice, thx. Its kinda MxM handles it...

But can you suppress the Message and force UX manually to set up the new HD?

yes add <Item Action="PrepareHD" Password="Xbox">Prepare New HD</Item> to the menu section of your config.xml and burn it to disc then select it from the menu and put in the password