I HAVE GIVEN THE POWER CONNECTIONS IN G41M-P26 FROM CPU WITH THE HELP OF USER MANNUAL,STILL IAM NOT ABLE TO SWITCH ON PC,BUT MOUSE IS GETTING POWER WHY?

NOT TOLD WHAT IS GOOD AND BAD
COMPUTERS ARE COMPLEX
SWTHING wild guess power button dead (switch)
G41M-P26 ???? 2009 ami bios.
not told what is connected to the mobo ,(all things)
and can not guess that.

You don't give enough information. You need to decide if motherboard is starting up - and you can hear hard disk(s) running and accessing data, or if everything is totally dead.

If the former the lack of a display could be a fault with your graphics card.

You need to see if the power supply is running, look and see if its fan is going and then listen to see if hard disk motor is running. If these are dead try a replacement Power Supply.
If you get some text or graphics on the screen when you first turn on, and before screen goes blank, that suggests it is running and the blank screen can be due to a software problem.

If you need more help, supply more info about the fault.
Cheers.

The most likely solution is to replace any Capacitors that have blown in the onboard power circuit. Look for a Capacitor that has got a very bulging top in the region of the power connector.

It may be a power supply issue. Try swapping a known good PS if you can, to be sure.

on the board is a jumper right above the pci slot (blue) with the pc powered off, move the jumper to pins 2 and 3, then wait 5 seconds, then move it back to 1 and 2. your bios is now reset :)

Initially you need to connect the PC power cord, connect the monitor to the power terminal and the display cord to the PC. Now connect the keyboard and the mouse to the specifed slots.
switch on and let the PC boot up, if OS is not installed then you need to know how to partition and then install the OS using the CD that was given to you. Once this is done the drivers to the PC must be loaded, is this is not given then you must download the whole package of drivers so that the PC hardware is activated to work. Finally install a good antivirus into the PC.
It is best to seek help if you are not aware of these instructions.

try sir first to scan your pc with a reliable and full operation anti virus, restarting pc usually is infected by virus.

welcome this is my first desktop ever owned.
DIY too. and done wrong, if quiet is the goal.
your centigrade temps are normal.
no goals told, gaming or what:??
if gamed fast, that makes huge heat and must be expelled. or things fail. hard. Heat is the #1 cause of electronics failures. (fans cured)
DIY steps
1:I buy a top brand case with huge slow spin fans 120mm and even larger the larger they are I can run them slower for same air flow.!!
I can also add my own fan controllers. to any PC, DIY has no limits.

2: the PSU is sold in vast types, and some like mine has USB port and and app that lets me set any thermal fan speed I want.
so we pick the PSU now and most PSU 99% run full speed all the time.(cheap) better PSU have 3 speeds, based on thermal sensors inside the PSU. learn to shop wisely PSU, is the answer.
Cheap PSU are full speed all the time, ever read up on Corsair?


3: MOBO some mobo like my beloved ASUS, Z270prime allows full fan controls of CPU and case fans. or set to auto mode.
some mobo (vast) do not allow that because they do not want to pay out warranty claims after you burn the VRM bank to *****.
Like OEMs modo do. all. most have zero controls allowed by you.
Asus knows we use huge fans, and we want to set the DIY fan rpm thermal rules based on the fans I WANT to use, amazing no?
ASUS is king, never MSI , Gigabtyes is good too..

your 4 pin fan jack is PWM controlled, modulated by the BIOS
this is one of BIOS many jobs here.
the 3 pin fan sys, is full speed all the time so use only large quiet fans here.
page 17 in your manual states

"if the mainboard has a System Hardware Monitor chipset on-
board, you must use a specially designed fan with speed sensor to take advantage of the CPufan control."

that means an option you pick day 1 from MSI.

I do not like MSI at all there manual is no good and faq missing
There are after market 3rd part fan control APP's that can work
for CPU only. google finds them.
frankly the choices are endless.
DIY desktops, RULE.
even water cooled and no fans at all is possible (PSU excepted)
here is extreme cooling up to 200mm fans,

https://www.newegg.com/p/2AM-000Z-00080?Description=PC%20case%20with%20200mm%20fans&cm_re=PC_case%20with%20200mm%20fans-_-2AM-000Z-00080-_-Product&quicklink=true

200mm

https://www.newegg.com/p/2AM-000Z-00089?Description=PC%20case%20with%20200mm%20fans&cm_re=PC_case%20with%20200mm%20fans-_-2AM-000Z-00089-_-Product

the bigger the fan the slower it can turn and not make any noise
and is decision #1, for sure,
also the PC may run great with just 1 large fan connected.
gamed, we have a free bench mark program to make the PC run hot to test the fan quality.

That switch is power activated - the kb and mouse are assigned to first one that starts and the second pc thinks that it doesn't have neither keyboard or mouse attached and freezes.
Before starting the second pc manually change the assignment.

please you first switch turn on