I installed Linux,and the PC doesnt standby

Some Linux versions often encounter problems with hibernation. That depends on the combination of which hardware you are using and which Linux distribution is installed.

Look at this posting for example regarding the same problem in ubuntu.

One important issue - and that is valid for all Linux distros - is, that your swap file has to be larger than the amount of RAM you have installed, because hibernating and stand-by writes whatever is in RAM to your hard drive. If you have 2GB of RAM installed, your swap partition has to be at least 2GB.

If you need more help, tell me which Linux version you are using. For now, your best choice is to search the forums for your distribution. There is a solution posted here, but since I haven't tried it, I can't guarantee that it's working,

Before working on system files, always make a copy of your original file in case something goes wrong.
>> sudo cp examplefile.conf examplefile.conf.bak

If you have any more questions, just come back here and leave a comment - I'm happy to help.