There are many elements which will affect your rating on the Playchess.com:
-computer
-engine and engine settings
-book
-good luck and bad luck
-your opponents


================= COMPUTER ===============================
This is simple. The better computer you have, the better is your rating.
If you can afford – get better computer.
If you are not buying new computer – look to improve in other things.
Single with excellent book will have better rating than Dual with bad book
(in the opening game can be won or lost and the computer speed is
not important then).


================= ENGINE ==================================
Good engine is the engine, which plays well on your computer,
write down your settings, especially if your comp started to play well.
Engine settings (like hash) will have also an impact on your rating.
Recommended hash size: 16,32,64,128,256,512MB
Some people also try 40,48, 96MB


================= RECORD RATING ==========================
You got record rating – stop playing, make cd-rom with your book
and write down your settings and put on this cd too, if there is any learning
file (shredder,hiarcs) – make a copy of this file and put on the cd too;
when you got this cd-rom in your hands you can try to improve something :)

for example:
I had with my Single (AMD2400 with 256RAM) above 2700 rating,
I was winning with everybody, the computer was playing really well,
winning draw positions against Duals, including my Dual. And what
happened next? I decided to improve… And I am around 2500 and
no idea why. It should be better now, right ??? But it is not :)
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