blank screen after RAM upgrade on HP 6510b

I've already tried HP customer service. I installed 4GB of RAM & now the fan just keeps running & the screen is completely blank?!?! I took the new memory out & put the old 1GB stick back in (under the keyboard) yet I still have the same results. I plugged in a VGA cable to an extra monitor, no luck. I tried inserting the XP OS disc, nothing. Before I had a power on/BIOS password but I can't even get to the point where it comes up? Can anyone tell me how to reset the laptop as I hope my BIOS has changed with the new RAM & I don't have a more serious issue. The laptop came with Vista, but I downgraded to the XP disc that came as well. I'm pretty sure I have the right memory b/c I ordered it from crucial.com; its DDR2 PC2-6400 CL6. Please any help/info is greatly appreciated.

If you have a add on video card make sure it did not get bumped during the ram install. You may need to re-seat it. Check all and any thing that may have become dislodged during the change over.

Thx Tinker but I my video card is integrated into the motherboard, not an add-on

I know on a Dell laptop you can hold down the fn key while turning on the power and it will boot into a diagnostic program. Does HP have anything like this?

I've tried holding down F10 & F8 (I cant remember which one took me into the BIOS setup but according to HP website one of those should get me to a diagnostic program) but nothing. I dont even get the 'beep' sound for the power on password prompt; I dont think its making it that far. I've reseated the RAM a few times as well as tried various configurations of RAM (only 1 stick in at a time, etc) but still nothing. I removed the RTC battery in order to reset the CMOS but that didnt work either. This is really starting to bother me b/c I think its something very simple I'm overlooking.

It has been a long time since I have had any memory problems. In fact the last time was with pc100/pc133 memory.

Your situation concerns me a little since I have a Compaq CQ60 -210. From what I can research it is virtually identical to the HP alternative. I am waiting for delivery of 4GB PC-6400 on Monday or Tuesday. I purchased OCZ memory from TigerDirect.

I will report back once it is installed.

Your problem sounds like an incompatibility issue to me. Suggest you contact Crucial support for assistance.

Pull all the memory and just turn the system on, but don't hit any keys. Does it give an beep codes doing this?

Excellent question.

Finally got it working. Thanks efc & rik for all your assistance; efc you may be right about the incompatibility as I dont think both sticks of RAM would be bad. I dont know how/why crucial.com would recommend the memory for my machine? Here's the steps I took:
1) remove both laptop & RTC battery for several hours
2) put factory RAM in primary slot (mine is under the keyboard)
3) powered on using only AC Adapter (leave the battery off to the side & when I connected the AC power the laptop turned on without me pushing the power button)

efc, let us know what happens when you get your RAM. Thanks again everyone.

bossdog22, I don't think it is a problem with the RAM to be precise.
Do this
Check the current RAM settings. You can use CPU-Z. Give us then the specs from the RAM installed (speed and timings that supports and then speed and timing that is actually running, which are not always the same)
Then give us the exact spec from the RAM you bought and/or the model number
Now, my sister had/has the same problem with 2 different laptops
1 is an HP, that my 5 year old niece run over it, so my guess that laptop has a bad motherboard now :p
Sometimes to get it to boot, we have to unplug the battery for hours (if not days). Since that was annoying she got a Toshiba that has Windows Vista. Sometimes the Toshiba would not boot up. The only way to boot it up is to disconnect the power, and the battery for about 5~10 minutes, then I connect the AC, and then I insert the battery. I don't know why it does it, but it is not related to the RAM. It is possible that it was coincidental that it happened to you with the RAM change, or the CMOS update triggered.
So, with this said, you might want to try again inserting the RAM (So you get the 4 GB) and it it does not respond again, remove all power sources for 10 minutes, then connect AC and turn on ;)

New memory installed. No problems encountered.

This reported in Belarc Advisor:

2814 Megabytes Installed Memory

Slot 'S1' has 2048 MB
Slot 'S2' has 2048 MB