It's not malicious, but highly obfuscated.
Find decoded script attached. PW: "infected".
Explaining in detail how to decode might take a bit long.
Here are the steps:
-put it into Malzilla's decoder window
-click on "Templates" and choose any browser (navigator)
-run script
-choose the second eval result
-copy the output (bottom window) into clipboard
-replace "____ (O000);" with content of clipboard in top window
-replace "eval (O0O0)" by "var naa=true;"
-run script
-that's it.
