I already wrote about Virtual disk API support in Windows 7. All that was based on beta so, now with Windows 7 RC in wild, some corrections are in order.
Microsoft decided to replace word surface with attach. While plenty of those changes were done in beta also (e.g. DISKPART), renaming of API functions was timed for release candidate. Since this change invalidates my previous code examples on how to work with virtual disks, here is new example that works with RC (but doesn't work with beta).
Usual practice for release candidate is to be code-complete - hopefully no further API changes will be done before final version.
P.S. This code is work in progress, in no way it is production quality.
[2009-05-03: There was bug with one parameter in code. On beta, that bug went unnoticed, but on release candidate it causes open operation to fail with native error 87. I updated source code so all further downloads will point to correct files.]
[2009-06-12: There was change in enumerations from beta to RC that I missed. Side effect of it was inability to permanently attach virtual disk. This is fixed now (to make it more embarrassing, I used correct code in Open and attach sample but somehow I missed to notice the difference).]