hi,
yesterday my sisters computing was working fine...but today when we turned it on no picture came up..just a black screen but lit up kinda (if ya know what i mean) me thinking it was the graphics card, put a another one in..but still it done the same..i tried her monitor on my computer and it worked!! and then i tried my monitor on hers and it didn' work!..i have no idea what the hell the problem is, lol...or what is making it do this.

Any help would be greatly appreciated.

Theres only 10 people that understand binary, those who do and those who don't.

Failure to boot can be caused by a number of different things but the bare minimum hardware required is:
Powersupply
Motherboard
CPU with HEatsink & fan
1 stick of RAM
graphics card (onboard or plug-in) with monitor
Keyboard.
Start your troubleshooting by disconnecting /removing all drives, pci cards, extra ram, USB devices, printers etc.
In "barebones mode" will it boot into bios and give a display? Any POST beep?
If no display or beep try booting with ram removed. Any Beep?
replace the ram and remove the graphics card.
try to boot. Any beep?
If the powersupply is shot none of the above tests will work.
To isolate which component is bad you need known good spare components to swap in/out.
Of course your problem could be something as simple as a card or cable slightly out of position. re-seating everything may solve it.

If it boots up in barebones mode then the problem is with one of the peripheral devices such as drives or PCI cards.

reconnect them one at a time with a bootup attempt between each reconnection.

If after testing you are still unable to isolate the problem you might have to take it to a tech. the other alternative is to start buying replacement parts such as powersupply, motherboard, cpu in the hope of getting it right before you run out of money.

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