Okay, the other day, I was being foolish, when I decided I'd open up my computer and Clean it up. After I was done, I put it back together, plugged everything in, and tried to turn it on..

No light came on, no fans, no beep, no boot, absolutely nothing happened.

So I opened it back up to see if I unhooked something accidently, couldn't find anything.

I tried replugging in both sides of the power cord, it failed.

I opened it again this morning, and i found a cord that isn't connected to anything..it's labeled p7. Maybe this is my problem, cause I dunno where the heck it goes. Can anyone help me please?

what kind of cord how many holes what size color etc what setup have you got. :bounce:

all I know is that it's a white cord with p7 written on it, and it's connected to other cords, all of which are plugged in to the cd drives or (the hard drive?)

My Computer is Dell Dimension, dunno if that helps any..

if this isn't enough info, I'll try and get more tomorrow, but it's bed time for me.

Welcome to TechSpot
The P7 is most likely a flat 4-pole powercord from the Powersupply (or PSU) that is probably a spare.
Check that all your CD-Rom, floppy (if any) and harddisks have such a cord attached. Furthermore, all drives need to have a flat cable connected to them, whose other side ends up on the motherboard. Make sure these are all seated properly.

If you cleaned your PC using a vacuum cleaner, you may quite likely have damaged your memory with static electricity. Just to be sure, check that all your memory-chips are fully seated and that the white safety-clips on either side are straight up.
Check that your graphics card, modemcard, soundcard and what have you, are also all properly seated.
If you have a Pentium 4, make sure that the square powerplug from the PSU to the motherboard has been connected.
Finally, when you power up, check that ALL your fans are turning.

I didn't use a vacuum cleaner, i Just blew the dust out with air, maybe a big mistake.

Everything seems to be connected correctly..

Well, I've noticed, when I plug my power cord into my computer, and open it up with it still in, there's a green light on one of the boards signifiying that it realizes that it is there. But when I push the button to start up, no light comes on, or fan or anything.

Is there something that connects that button with another part of the computer that could have possibly been unhooked?

Also, when I plug my moniter into my computer, the moniter registers that it has been plugged in.

The start-button on the front of your PC leads (with a very thin, 2-wire cable) to your mobo. This plug is probably labelled "PWR" or "Power". Check in your mobo-manual that this cable is connected to the proper pins on the mobo. While you are at it, in the same cluster you will find Reset, (internal) Speaker and HD-LED connections. These are easy to disconnect inadvertently.

Okay, I've got questions now that may seem pretty dumb, so remember I have no experience in this.

What is a mobo-manual? I know mobo means motherboard, or I'm guessing it does, but I'm not sure where the mobo-manual is at.

and..proper pins? I'm not registering what you mean. I checked out my PC..not sure.

And I couldn't find a two wire cord, also I can't even get to the place where the opposite side of the on button is in the computer..

I couldn't find any of the other connections either, but I'll keep looking. Thanks for putting up with a slow person.

mobo = motherboard
manual = leaflet/booklet/handbook that describes the motherboard.
These 12-20 gold-colored pins, in rows of 2, are normally at the edge of the mobo, and have thin wires leading to the front of the PC for On/Off, Reset and control-lights.
If you pulled any of these off during cleaning, the PC won't start.
Check your manual, or download it from the mobo-manufacturer's website.
Also, fill in all the details of your PC under "User CP" top left of this screen.

Okay, thanks I'll have to check everything on my pc out though (later) I have to go to work for now. I'll get back to you tomorrow hopefully.

Hey, if the memory chip, or whatever the thing is that is held by white safety clips is damaged OR not seated properly, will the computer not power on at all? I'm guessing it will still start, but do nothing.

If your Dell PC is still under warranty, I would advise you to bring it back, rather than you poking around in it.
If anything has become unseated, chances are the PC wont start up.