Since there is no video, but there is power the problem is probably with either the video card, RAM, motherboard, or a conflict between the MB BIOS and videocard - and a BIOS problem is not likely since she's probably not using a professional workstation video card. If there is bad RAM or a bad board (motherboard or video) then there's not much that can be done except exchanging the problem devices.
Since there is no video, but there is power, there are two possibilities that we can assist with: properly reseating the RAM and/or properly reseating the video card.
While the primary problem is still no video, a symptom of an improperly seated video card, the attempted correction is to properly seat the video card. Since there is power but no video, this is the most logical path to pursue.
So the primary problem at hand is to reseat the video card AND ensure that noiiie's equipment is also protected regardless of whether it's damaged and assuming that it's not.
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noiiie, since your experience with PC's is very minimal, follow these instructions and precautions.
Most newer motherboards have support for On-Now technology. Since the motherboard can turn on if any component (AGP, PCI, RAM, etc) is installed or removed while the power supply is connected, you must ALWAYS DISCONNECT the power supply cord between the electrical outlet and case while working on newer motherboards. Otherwise, components and the motherboard may be damaged if the motherboard powers up while you insert/remove components.
You should never work on carpet because of the static that is generated by carpet (even if you can't feel it, it's always there).
If you work in the following way, you can expect the following results.
If you press at an angle, the board is likely to move and the board is not likely to seat properly.
If you do this on carpet or flexible surface, the carpet or support compresses as you insert the card and the card may not seat properly.
If you do this without having enough clearance for the card bracket, the card will not seat properly because of the physical interference of the card bracket with the surface below the motherboard.
Find a table or countertop to work on which is both stable and rigid and a piece of cardboard at least as big as your motherboard and some strong tape. Setup a temporary work area on the table or countertop. You should securely tape the edges of the cardboard to the working surface with duct tape or some other strong tape to ensure the cardboard doesn't move while you work on it. Then place your case on the working surface and your motherboard on the cardboard. The back edge of the motherboard (the edge where the keyboard, mouse plug into and that would sit at the back of the computer case) should align with or slightly hang over the edge of the table/countertop by no more than 1/2". This will ensure that when you insert an AGP or PCI card that the card bracket doesn't interfere with your working surface and will allow the AGP or PCI card to seat fully in the slot. As mentioned before, when inserting a card, place the thumb of each hand over the top edge of the card to be inserted such that each thumb is over each end of respective slot of the AGP (or PCI) slot so that proper pressure is applied evenly on the upper edge of the card where it most matters. Then press firmly downward while being careful not to slip or apply uneven pressure -- don't be afraid to apply enough pressure to make the board move into the slot.
As for the remainder of the setup, the only connections you need from the case are the wire connector from the power switch to the motherboard and from the power supply to the motherboard. Remove any LED connectors or any other attachments. Only a CPU, CPU fan, power supply, RAM and video card need to be connected to the board. You don't need a mouse or even a keyboard to get an initial video post. You will still need the power switch connector on the case chassis to startup the computer.
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In the future, concrete or cement floors (like in a garage) are much better than carpet because of the lack of static and grounding capability of concrete. If you ever try this again, setup a temporary workspace in a garage (over bare concrete) if possible.
In the future if it's not possible to work on concrete, find a table or countertop that is both sturdy and rigid (not a card table) and preferably not on carpet.
For your work surface, place a piece of flat cardboard or a piece of unstained, unfinished plywood which is at least as large as the motherboard (and 3/4" thick if possible) on the table or counter. Use this place to work on your board. Since you don't have ESD training, before you touch anything in your PC, always touch the chassis (unpainted metal parts) to ensure you don't have static. Any body movement (arms or legs) generates static potentials that can cause Electro-Static Discharge (ESD) damage to any electronic component. Some ESD damage causes nearly immediate component failure, other damage doesn't cause a full component failure but causes component degradation by partial failure. This last type of damage is pernicious and frequent by amateurs and is called latent damage, because it's often not apparent until later or because the partial failures cause intermittent problems. Because of partial component failures manufacturers always recommend ESD protected work areas and personal protection when working on electronic components.