How do you solve lenovo G550 Whitescreen problem.

The WSOD, (white screens of deathh(sic))
a very rare thing, and the 2 beeps.
step one, dump out the huge battery and test with only AC power pack. battery this old are bad and short, remove it first. first things first rules.

rule 2, carbon14 dated by me at 2009 made, so the RTC coin cell battery
can be bad (pink bunny spec is 7 year design life)

rule 3 , If BIOS screen are ok, my guess no, WSOD'd.
2 beeps, the silly manual on it does not cover beeps.
beep codes very by model and year and are poorly documented.

i hate lenovo's I buy dell/hp we have real service manuals on our PC USA, by American and win.

or at least ASUS of Twain. (nationalists are cool)
Lenovo's chapter on troubleshooting is useless. for sure WSOD or any hard failures are not covered at all,....
The Infamous SOLDER BALL :ERA:

the WSOD might be the BGA, GPU chip solder failures.
back then they made millions of PC that must pass USA no solder lead rules, no Pb lead. and failed by the millions, 2008/200.

white-screens or worse lines on screen or dead.
twist the screen bezel gently does the screen change.
now do that to the base(GPU side) and does it change. if yes. think bad GPU chip BGA.
BGA = chip with ball grid array pins.
Do more tests?
see left side, see 15pin Dshell VGA port? connect this to a real monitor, VGA get better results? there is hot key for turning on both. page 12 in your manuals states and I quote:

"Press Fn+F3 to shift to other connected display devices."

just key doing that , every 10seconds to see if VGA wakes up.
on many PCs this Press, toggles as 3 or 4 ways below:
internal screen
VGA ext.
both
auto.

that is all I have, more tests are possible and more complex.

one more overheating, clean the vents of lint.
its got a decade of lint inside. so....

1: big battery out (leave out until PC works again)
2: new RTC coin cell, the old one is bad or near.
3: clean the lent out.
4: reseat ram sticks.
5: test with external monitor , VGA port.
6: do the long reset trick>?
a: big battery out,, ac pack unplugged. push power for 30
seconds, release.
b: put only AC power pack fully connected now, and test PC. beep still?

7: last test is complex, we unload the motherboard.
of all modules (any can short, is why)
and test the PC stripped down to near nothing.
see photo of HP stripped to zero.

http://www.pcdied.com/BIOS/blink-w-scr1.JPG

8: remove all ram sticks and test them all 1 by 1, in bamk 0 as the book on your pc shows for RAM population.
warning my PC has 2 top and 2 bottom raM BANKS.
on mine the keyboard off reveals bank 2(RTM is wise)

9:Ask real lenovo forum what 2 beeps mean?
fixya is not Lenovo.

The key to diagnosis, is know things short out, not just open connections like simple ram sticks can do.
(dirt caused on sticks.)