Screen dead after ram upgarde

Hi there,

I have a lenovo thinkpad z60m-2529 with 2 RAM cards of pc2-4200x512mb.

I tried upgrading the RAM in my laptop and when I switched it back on my screen was dead.

To upgrade, I replaced one of those cards with pc2-6400x1gb. (I understood that the pc2-4200 and pc2-6400 will work together at the slower speed).
When I switched on the laptop afterwards the screen was blank, so I removed the new RAM and put back the old, but it still doesn't work.
I also connected an external monitor to see if the problem was specifically the internal screen. The external monitor stayed blank.

Any advice help or suggestion would be appreciated.
Thanks

So each stick individually has the same problem, and so do both of the old sticks together? It sound like you either haven't installed the RAM correctly or have knocked something loose in your efforts.

Replacing the RAM seems easy enough. I suggest looking over page 65 in this PDF. Click on the download now to view.
http://support.lenovo.com/en_US/de [...] MIGR-61364

You may have not snapped the RAM into place. Make sure the battery and the power plug are both removed before attempting any hardware changes. A blank LCD is a symptom of no or incorrectly installed DIMM's. I suggest trying it again with the new RAM and ensure you are properly grounded.

Sounds good.