well a quick first guess would be did you have the computer on a carpeted floor when you had the case open, you might have ran into a little ESD on the memory when you had it open you be remarkably surprised at how little it takes to ruin memory. Secondly another problem could be a reversed (backwards) connector which would give power through the pins but would not send correct signals

......What happened to you is not unusual....I have had this happen many times and usually if I take the machine completely apart and look at each piece...connectors and all and then put it back together....while singing to it softly it will come back alive and act nice....at least for a while...and if you need an excellent Diagnostics program that can tell you anything about your computer and even have live links on the summary page to direct you to driver updates and downloads! you can get The Lavalys Evergreen Home Edition..... http://www.lavalys.com/ try it! you'll like it!....Mal...

I am homing in on the problem....as bama.mal eluded to, connections can be troublesome in general. I had take all apart and it hadn't helped.....

Then all of a sudden the pc started working - got the green light, p/s fan stayed on, etc...WOW!! Trying a few times, I thought all OK now.

Then it happened again and I've narrowed it doen to the power switch/wires or wires for the LED's for power or hard drive.....I think there is a short probably in the power LED wires, just need to get some time on it.

thx all!!

will post again once resolved for sure and the PC has run for a while with no troubles (at least the ones noted in this post!).

I found a power supply socket on the mothernoard, with three wire slots. it is as wide as 3/8 to 1/2 inches. You need to make sure power supply is connected to it neatly. Otherwise, system would not boot even to bios screen.

Chris

i had a situation where my hp pavillion slimline s3400t didn't boot up. blue light on the tower, monitor seemed to be working -- yet when i turned it on the monitor just read "vga, dva input: no input signal" and the monitor went to sleep. when i was under the 1 year warranty i sent it back and had it fixed (don't remember exactly what was wrong, i do know the front i/o port had to be replaced). Then 4 months later, exactly 1 month after the 1 year warranty expired, the same exact thing happened. and of course HP wouldn't help me unless i pay 100 bucks for phone support, then an additional 50 for hardware support, to which i hung up. wouldn't transfer me to a supervisor even after calling 3 separate times.

So i looked through the paperwork that i originally got when i bought the desktop. i noticed a small card that read something along the lines of 2 year hardware extended warranty, please fill out and send back immediately with no credit card info required. I was able to fill this out online (for free) and then called a day later to get support....and was able to get support because now i was magically covered for another year (2 year warranty - 1 year into the purchase = 1 year left). went through the motions and now i'm waiting for my package to send to HP and get the desktop fixed -- FREE OF CHARGE. my suggestion to anyone reading is that if you purchased the deskop less than 2 years ago, go through your warranty information again and see if you can sign up for this hardware warranty. complete bullshit because HP didn't tell me that i could do this when i called them 3 times (although i obviously know why they didn't). I also read somewhere that if they fix the same problem twice and it happens a third time, you can get a refund. anyone hear something similar?