About the 3rd post

its either a hot videocard/cpu or a bad ram


about the bad ram part:
download memtest86+ from http://www.memtest.org , copy to disk or burn to cd, reboot and let that run for at LEAST an hour
if it gives no errors, perhaps let it run the entire night

if memtest gives you errors, its MOST probable your Ram, either that, or a small chance its the L1 cache or motherboard memory
if it passes this test, your Ram is ok, and the crashing problem is somewhere else

next step download Prime95 from http://www.mersenne.org/freesoft.htm
prime is normally run worldwide to find more prime numbers
but it also has a 'torture test' function
this stresses cpu, ram, harddisk

again let prime95 run for at least an hour, if still no errors perhaps let it run during the night/workday
if it gives errors here, its either the Ram (but than memtest should give errors too) or just general instability

if both of these are error free, the problem lies within WoW probably... cut/paste your /interface and /wtf folders to somewhere else and see if that solves the crashes
if one or both of these give errors, try switching out ram modules to see if 1 or more are defect, if so RMA them back and get some new ones