I was using a program called simple center on my pc when the screen went black restarted my computer then all of the sudden showed the message error loading operating system and shows that message everytime i restart i also cannot press f8 during start up it does nothing does anyone know how to help me with this problem....

Hello, irish. Something has damaged your boot sector on the systemdrive. You will need the Recovery Console from your installation cd, and the commands you should run are:
chkdsk /r -see if the sys will start after this completes; if not, then:
fixboot

thank you very much for your response i am not that knowledgable in this area of copmuters this computer was built for me by someone and i have no installation discs and i cannot find a way to bring up a command prompt or anyhitng like that all i can access is the startup and boot menu's i tried taking my harddrive out and putting another in and that is not working either any ideas??

Irish, the message "error loading operating system" is actually written into the MBR on your hard drive, so your BIOS was actually reading from the hard drive to get hold of that message; the next step which is locating the OS [via C drive being marked as Active] was done also, but the files which are used to load the OS itself were not loaded or found.
You need to borrow an installation cd and use that to get into the Recovery Console. Try to get one which matches your service pack number ..eg SP2. Your first hd is probably physically ok, it just has some file damage.
I find it strange that another hd would not work... what msg did you get with that? Did it have an OS on it?

you need to have the disc installer for your OS, ask a technician to help you re-install OS..but don't format just choose "REPAIR" during the installation so your files will be saved

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