As soon as turn computer on it says operating system not found -- i can get it to go to one other thing and it ask for HDD user password which i have no earthly idea what it can be

1. i hope you have backed up of all your data from the HDD.
2. format the HDD and reload the OS - but this time, make sure that you have atleast 2 partitions.
3. keep all your important in the second (non-system) partition.
4.after you have reloaded the OS, please get a good anti-virus and anti-spyware application and scan your computer regularly with them.

A sudden display of operating system misplacment is an indication of a wiring disconnection especially to computers that are connected to a mainframe server situated elsewhere. The wiring connecting the display monitor should be checked for readjustment. Second, labtop computers suddenly displaying operating system misplacement indicates a hardrive maladjustment caused by frequent movement of the device or collision between devices. Check the device for displaced parts especially the harddrive. Third, the operating system malfunctions with the insertion of a disk medium in the disk driver that is capable for altering the entire configuration. check the disk drivers for remaining disks, removing and performing a restart of the computer afterwards. fourth, an intact device without missing parts or broken parts observable woould require operating system reconfiguration depending on the message that is displayed on the screen.

fixing a computer without hardware part damages

First, a computer requirinng reconfiguration though every part is intact is performed by reinstalling a new operating system program. Acquire the operatimng system program disk to reinstall. A functional disk is indication that hard drive is missing especially if the disk driver is functional

Note
A missing harddirve to store the operating system would least produce any indication of functionality when a disk is inserted into the computer driver.

A missing hardriver storage medium or crashed due to excess heat or collisions would have caused an operating system to become volatile.

A crashed harddrive storage medium requirs a missplacement storage, also requiring an operating system reinstallation soon after the storage meduim.

The harddrive was wiped from the computer, you have to reinstall it either from the disk that came with your computer. HDD is the password for the harddrive, is it a SATA harddrive