Powers but I get a black screen and blinking LED

[Lyndsie]

I have a problem.  I used one of those air can things to blow some dust out of the inside of my computer and I also used a little battery vaccuum on it.  I live in the desert and we get a LOT of dust.  Now, when I turn it on, it turns on, the fan is running and the power light is steady green, and it sounds like it is starting up, but instead of the sign on screen, the screen is black and the monitor light and keyboard num lock lights are both flashing green.  It is a Compaq Presario 5300 with a celeron processor, 128 MB RAM, 80 GB HD, running Widows XP Pro.  That's about all I know!  I am not super-tech-y lol, but I know enough about the workings of a computer to installl a new HD (about a year ago), and a new CD burner (about 8 months ago).  My next step was to add some more RAM, but I don't know where I stand now.  Any help is very much appreciated!
Lyndsie  

[GX1_Man]

Vacuums create ESD, so hopefully you didn't disturb anything. Did you shoot it directly into the fan blades while spinning? Also not a good idea. Hopefully you just knocked something loose. Make sure the fan is firmly attached and spins when the computer powers up. Remove and reseat the RAM modules and any cards in slots. Let us know.  

[Lyndsie]

Thank you SO much!!  All I had to do was change the RAM module to the other slot, and now I'm back on the sign in screen!!  I thought it was going to be more complcated lol!  Newbie here, obviously  

[GX1_Man]

Glad you are up and running.