Cannot turn computer on, motherboard LED on.

[mattlolwtf]

Basically it's mostly in the title.
But details:
Dell5100

I tried to add RAM today, and it was incredibly dusty, I somewhat cleaned it with a swiffer duster gently. Then I went out bought it and came back. Plugged the card in, and bam, computer doesnt work. I assumed it was the card, so I took it out, still having 1gb in it, and it still doesn't power on. I've been on the chat and it sort of helped but not really so here I am. Just ask for any details or info on what happened.
Does anyone think it might have been the act of opening it, releasing dust somewhere and clogging some stuff?

[Carbon Dudeoxide]

Take out all the RAM in the system then put one back in. Make sure you put it in correctly and that it locks in place.
Turn the computer on.
If the computer still has troubles, remove that one card and put it in the other slot and try again.
If the problem continues, do the same with the other card.

[mroilfield]

Using a Swiffer Duster inside a comp isn't a good idea. Those things build up static electricity really fast. The best thing to use for cleaning dust out of a comp is a can of compressed air.

[mattlolwtf]

I removed all the cards and put in one of the ones I knew worked, tested each slot, and it never once gave any signs of power.

[JJ 3000]

You may have accidentally dislodged one of the motherboard's power connectors. Make sure all of the power connections to the board are tight. Make sure that the power switch lead is on the pins. Make sure you ground yourself before touching any internal components. Make contact with the metal case the whole time you are working inside. Static electricity can fry your motherboard!