Windows 7: Dual boot system has my system down

i have a new pavilion dv7t, and after trying to set up a dual boot system, it refuses to restart. i have 7 home prem. on the c drive, and wanted to put win 7 ultimate on the "a" drive. but after a couple of reboots, on the last reboot the computer gets to the initial prompt, and then just has a flashing cursor in the upper left corner and will not go any further. i have run memory diagnostics, hdd diagnostics, start up diagnostics and runup diagnostics and although every single one of them passed with no errors, it still will not boot. the computer is so new, that i haven't had a chance to make boot disc's yet, because i didn't have any writeable disc's on hand. is there anything anyone can tell me that can help?

"A" drive is your Floppy Drive.

Try this:

Startup Repair
Note: You may need to do startup repair 3 to 4 times.

System Repair Disc - Create
System Recovery Options
Repair Install

drive "a" was a floppy drive 15 years ago! lol!!! drive "a" is a partition i setup for another opsys. i will continue to try the startup diag. thanks.

See if it finds an installation other than your Home Premium to repair when you boot into DVD/Repair CD "Repair my Computer."

If not, then you'll need to mark Home Premium active to get it started up. Boot the Windows 7 DVD, press Shift F10 to open a Command line, type:

DISKPART
LIST DISK
SELECT DISK # (replace # with HP HD)
LIST PARTITION
SELECT PARTITION # (for HP partition #)
ACTIVE
Exit

Now return to Recovery Tools list to Run Startup Repair up to 3 separate times with reboots to start HP.

Once in HP, explore the new partition to see what was installed. Change to another drive letter in Disk Mgmt. Try running the installer from HP again to install to other partition. If this fails, try booting from DVD for install using Custom>Drive tools to format partition first. Let us know the exact fail point and what the error message is.

Drives A & B are Floopy drives still today.

Because drive letters A and B are reserved for floppy disks... it's trying to boot to a floppy drive that probably doesn't exist on your system. In fact, I'm a little surprised it let you assign those letters at all.