Have a dell optiplex 760 bootmgr is missing how do i fix it

The display will show no signal or no sync or NO cable connected errors, no display model stated by you.
but first is the PC, it is dead.
does both fans in PC spin, heard? and seen and felt to blow air?

if not that is a DEAD PC.
and has many cause,(computers are complex but here goes)
1: ;PSU dead.
2: power button wires fail off or mOBO jack.
3: PSU overload by any thing inside the case, shorted.
the tests are here. called strip down and bench testing.

do the long reset first (AC cable pulled)

http://www.pcdied.com/PSU/strip-down-testing101.html

How to Reset BIOS or Admin Password Dell Optiplex 760 780 745 755

This is a symptom of a failed hard drive or corrupted operating system. You can try to reinstall Windows however any errors in doing so may indicate your drive needs to be replaced. Online Virus Removal 39 99 Online Virus Removal and Online PC Help

http://pcsupport.about.com/od/findbyerrormessage/a/bootmgr-is-missing.htm


HERE IS SAME GOOD READING FOR TROUBLESHOTING.

You can download drivers for Dell OptiPlex 760 by using the following link:
http://www.dell.com/support/home/us/en/04/product-support/product/optiplex-760/drivers

GuruAid.com

That is the file that your computer looks for to Boot up the operating system software. Either your OS (operating software) is corrupted or your hard disk drive might be defective. Here is a link to your model:
ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/esuprt_optiplex_desktop/optiplex-740_user%27s%20guide_en-us.pdf
Select the appropriate model and then view diagnostics or troubleshooting links to see if your hard drive is bad. If the diags pass on the hard drive test, then you will need to reload software.

http://pcsupport.about.com/od/findbyerrormessage/a/bootmgr-is-missing.htm


SAME TO READ ABOUT THE PROBLEM.

most likely

reinstall windows xp pro. in different folder
and keep all the files

Got some From DELL web ,Good Luck with it
http://accessories.dell.com/sna/category.aspx?c=ca&l=en&s=bsd&cs=cabsdt1&category_id=6175&~ck=anav

http://support.dell.com/support/edocs/systems/op760/en/sm/mtindex.htm
Got You Tech Guide Book http://www.dell.com/downloads/global/products/optix/en/Opti760_Tech_Guidebook_July_1_2009_Sustaining.pdf