sytem hangs everytime

R

my sytem hangs after sometime,say within 20 minutes after logon.
this problem starts since last week.
i haven't changed any hardware....

i installed nvidia ntune last week and now it has been uninstalled.
i did a tuning with ntune but it didn't alter any system settings.
because it says that it only works with nforce2 or later.
do u think it is the problem for the hanging??

please help me...
i took almost all my hardware parts and reinstalled in my motherboard.
but no use, still my sytem hangs ...
also i did a tuning with tune up utilities 2007..
my config:AMD athlon 3400+(2.2 ghz)
512 MB ddr ram(256*2)
sapphire pure element motherboard
geforce 7300 GS
40 gb HDD
cd rw+dvd combo

or do u think its the problem of the operating system..
please help me ..its urgent...

try restoring your system to the earlier days before u installed nTune or the days u remember in which ur system was working fine

Try running ur PC on both RAM sticks individually to see if one RAM stick is faulty.

Try running ur PC on both RAM sticks individually to see if one RAM stick is faulty.