Does the menu appear with the "Last Known Good" option?
If so, does it boot successfully if you select that?
Did you just add or remove any CD, DVD, AV or disk-related software?
STOP 0x7B means that the boot sector is okay, and it pointed to a boot loader which started the startup process - at some point after this, the kernel was unable to access a device tagged as "necessary to boot".
It could be:
- a disk problem (hardware)
- a disk controller problem (hardware)
- corruption of drivers on disk necessary to boot the system (disk corruption, fix with chkdsk)
- absence of a driver tagged as "boot start" (installation or removal of software that refer to non-existent .sys files)
MSDN: Bug Check 0x7B: INACCESSIBLE_BOOT_DEVICE
(See "Resolving the Problem" section)