Try this BIOS factory reset

Hold down Ctrl+Home, then hit power button.
keep holding Ctrl+Home until "EZ-Flash" start. (May have to hold for 60 seconds, or more, you will see keyboard lights flash and then say on when it starts to back flash BIOS)
Now wait until the factory shipped BIOS flash is finished, at the end of this process, it will say "restart in two seconds".
Your laptop should shut down on it's own (it's really important not to interrupt this process), and now you can try to start the PC.
This may work, if your BIOS is corrupt (May be your issue), will back flash your BIOS.

*This operation will reset the BIOS to the factory installed BIOS*

PS: Not sure if this will work, but give it a try.
Good luck my friend.

If the system was working before you took it apart and all the hardware is still working okay, it may just be a problem with the assembly, and below are some ideas with these assumptions.

1. Make sure the memory is plugged in well, and try one module at a time in different slots.

2. When you take it apart and put it back together again, make sure the cables look okay as well as are plugged in correctly since there have been some posts for other models from people who have either had damaged cables, or cable installation issues causing 'no post' issues.

3. Consider unplugging any unnecessary items or devices that could be related to this like the hard drive, battery, extra memory modules, and anything else that could be related to try to isolate the problem more.
If you've never had to disconnect any items though, you probably don't want to touch them for now assuming everything is still connected okay from when things were working, but still might need to be checked later on.

4. Make sure nothing is shorting out the motherboard and watch out for screws that are too long in the wrong places and anything else like this.

5. If nothing works, you probably know you can send it to ASUS for out-of-warranty service too if it's really necessary which hopefully will not cost too much if it does not require any expensive part replacements, but you will not know this until they take a look.

Good luck!

Did you ever get your g46vw running? If you did what was the issue.

You will most probably need a factory reset, just as @GottiBoi55 said.
I had the exact same symptoms like you yesterday and did this (with ac-adapter installed and battery installed):
HOME (hold) + CTRL (hold) + Power (tap)
It did require me to install my original HDD (my SSD wouldn't work) and a BIOS that I renamed to G46VW.BIN (I downloaded v209 from Asus website) placed in C:\ root.

The screen should magically start up with a blue interface for factory recovery.
I did do it a couple of times till it started.

EDIT: Memory combinations didn't do anything for me.

@GottiBoi55 THANK YOU SO MUCH!
I had exactly the same problem: power light ON, charging light ON, HD spinning, no Keyboard light, no boot.
Doing the BIOS Factory reset solved it.
So again, THANK YOU VERY MUCH!