Re: vostro 400 o/s is vista buisness

Hi inkman_returns,

Do you see any light on the Power button?

Do you get to hear any beep codes?

Disconnect all external peripherals except the keyboard, mouse, and monitor (for desktop systems). Peripherals also include external storage devices such as flash drives, USB devices, cards etc.

Drain Mother Board power about one minute (until MB lights turn off, which can take from 20 seconds up to one minute).

Make sure that the monitor is receiving power and that it plugged into the correct port on the video card. For SLI systems, the correct DVI port to be used would be the one on the primary (upper) video card, the one to the left looking from the back of the computer. This port can also be used for single card configurations.

http://dell.to/17nnylu

From the above link click   Manual and Documentation and Service manual to access  reseat/remove section.

** NOTE: Please ensure that the power cable of the computer is disconnected before opening the chassis. Refer to the Service manual for assistance on removing or replacing the internal components of the computer

Remove all the memory sticks (found next to the CPU) and attempt to POST the system using one memory stick at a time on Slot 1. Reinsert all memory sticks, and make sure that their connection to the motherboard is optimal. If after doing this the problem reappears then you may have a defective memory slot on the motherboard

Clear the CMOS settings: 

Perform different video configuration tests: make sure the video card(s) has/have the proper power connections from the power supply, reseat the video card(s) and if more than one video card is present, try them individually.

Remove all but the essential components (one memory module and one Video Card only) including, WiFi adapters, TV tuners, Optical Dives (ODD's), Hard Disk Drives (HDD's) and try to turn the computer on. 

Try running diagnostics:

• Turn on or restart the computer.
• When the Dell logo appears, press <F12> immediately. If you wait too long and the operating system logo appears, continue to wait until you see the Microsoft® Windows® desktop, and then shut down the computer and try again.
• When the boot device list appears, highlight Boot to Utility Partition and press <Enter>.
• When the Dell Diagnostics main menu appears, select the test you want to run.

Awaiting your response!