probably itz either
minor case of software corruption/improper ground/cpu fan..or
major case of faulty or defective main board/ram/daughter or addon card(s)..
..plz do check the following as in order:..the Hardware part
1)a) inpower on mode, open/unplug the data/vga cable of the monitorfrom cabinet..see if raster or 'osd' is appearing on the monitorscreen..if so monitor is ok..else replace the monitor and see..[notapplicable in case of laptop]..b) in case of laptop try to getoutput from external display unit/monitor using vga port..if there'sproper display in there..the problem is probably with either the 'lcd'or 'ccfl' or 'inverter circuit'..
2) if u hv a graphics card, replace with a standby or onboard and see..[not applicable in case of laptop]..
3) unplug mains supply..pick open/remove the cmos battery..check (above +3v)..resit..
4) see ifthe ram(s) is loose/faulty..open clean/remove carbon & oroxide formed on the teeth with an eraser n resit it..or replace with astandby n see..
5) a) see if ur hdd is noisy or emitting any 'ticking' noise (like 'tuk tuk' or 'kirr kirr')..
b) or if the system is not supporting either the newly installed device or itz software/driver /firmware
if so, u need either a fresh os installation or ur hdd is likely to b replaced..
6)remove/cleandust neatly..dust is non-uniform in nature n may cause jam/shortcircuitry/excess resistance n many more..resulting an increase in heat..
7)open the CPU Heat-Sink with fan out of the socket..put some "Heat SinkCompound" (available in local electronics chip level spare market)between the cpu/processor and the CPU Heat Sink *** fan..resit/fit ittightly in position..
8) on main/mother board..see with a debugcard for mb error..may b short..look for defective capacitors(espabove1000mfd)/mosfets..go through the mb's south bridge n the circuitlie around atx connector..the crystal clock generator (if cpu isn'theating up)..
9) [in case of desktop] the smps itself may bdefective/faulty..check the outputs of smps viz. 0v (black~ground); +12v(yellow); +5v (red, green~ps-on, violet~pg& grey~sb); -12v (blue);-5v(white); +3.3v(orange)..the 'oscillator and error amplifier ic',or pwm switching regulator circuit..look fordefective protector-transformer/resistance (esp 4.7k)/mosfet..check the battery n adapter [main power], in case of laptops..the Software part:..
1) hva licensed and UPDATED antivirus installed (i prefer avg/kaspersky,remember, without updation a full version antivirus is useless)..
2) download, install n run microsoft kb890830..http://www.microsoft.com/downloads/details.aspx?FamilyId=AD724AE0-E72D-4F54-9AB3-75B8EB148356&displaylang=en
3) download n run Startup Control Panel..http://download.cnet.com/Startup-Control-Panel/3000-2094_4-10039330.html
..'remove allthe unnecessary startup items from here..(if u can't find what toremove, post me/us in ur comment with all the items listed in each nevery tabs herein)..
4) remove all unnecessary software from add/remove programs..
5) download, install n run 'Advanced System Care Pro'..http://download.cnet.com/Advanced-SystemCare-Pro/3000-2086_4-10399324.html
6) disable the following:..
a) 'AutomaticallyRestart' right click onmy computer->properties->advanced->startup nrecovery->(un check on the) Automatically Restart;
b) 'ErrorReporting' right click on mycomputer->properties->advanced->errorreporting->disable error reporting->(uncheck on the) 'but notifyme when critical error occur'..
7) Increase the size of Virtual Memory, Initial: 1440; Maximum: 2880
if u r not a professional, always better to seek advise from ur system admin/vendor....