I have a hp pavilion 9720us laptop. I have the error message operating system not found. It was woriking perfectly until I inserted a usb flash drive. It then went to a black screen with the error message operating system not found. I have tried taking the cmos battery out didn't work. Removed harddrive didn't work. The harddrive doesn't show up in bios. I tried to run the diagnostic test it says no ide detected. Plesae some one help. Could it be my flash drive destroyed my hdd?

Ok when do you get the message about operating system not found? Have you tried resetting the CMOS? What settings do you have in the CMOS/BIOS setup for boot order?

Do you have any type of boot CD or recovery software?

Do you have another computer you could download UBCD4Win on and build the boot disk. It has partition recovery, file recovery, antivirus applications and boots a windows GUI to work from?

i think your usb might be coruppted

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