when I put my computer into sleep after few minutes without any instruction its automatically getting on. what would be the problem ?

Question

e.mccormick · Answer

If it detects any keyboard or mouse activity, that can turn it on.  Also, a sleep mode can be set to wake on lan activity, so just the basic operation of a network can wake a machine if that mode is enabled.

The next question is, why use sleep mode?  Unless you have some specific reason not to, like you will be using it again very soon, a shutdown is better than sleep.  Sleep mode can retain errors as they develop.

anonymous · Answer

In Control Panel, there is a setting that makes the computer open after a few hours. That's a possibility too

anonymous · Answer

@e.mccormick  what is mean by "wake on lan activity".

and many times i keep my computer into sleep because while work I take frequent breaks.

anonymous · Answer

@abb50 I has thoroughly gone through all the settings in control panel relating to power options and sleep mode etc. but my problem is not solved.

e.mccormick · Answer

Usually wake on LAN is a BIOS setting, but sometimes it can be changed by a utility inside the machine. The utilities are most common in laptops. http://en.wikipedia.org/wiki/Wake-on-LAN