The Windows may not start due to some reasons. I'm thinking that your computer isn't damaged and it is just some error with the windows configurations or some simple errors. These tips could help you repair your computer yourselves:
First thing you have to check the power supply.UPS
Look at the UPS if you have one. If all other peripherals connected to UPS are working, UPS is fine. Check the back of the system unit to see if the fan on the cabinet is rotating (You don’t have to open the unit to see this.) If it isn’t rotating your SMPS is not functioning. This means you need to replace it. It will be better to get it to a repair centre. If the fan is working fine, continue reading to find what is really bugging you.
MonitorCheck your monitor. If want, try connecting it to another computer. You can read on if it is working perfectly.
System UnitIf your computer was disconnected power when windows was in sleep mode windows may take some to start up next time. I don't know if this is normal. But it hasn't caused any problem to my computer! Wait for 5 minutes. Yes it could take that much time.
BIOSYou can try these and find if the trouble is with your hardware. You can do this if the power indicator/hard disk power indicator on the system unit is lit and there nothing in the display. If the system power was switched off before shutting down windows you may damage BIOS and cause boot failure on your system. You could repair by while clearing the RTC (Real Time Clock) RAM in CMOS (I don't want you do this if you really do not have any previous experience) by erasing the RTC RAM data, the CMOS memory of date, and system setup parameters will be lost. You can find more details in your motherboard’s User Guide about this (Method differs with different motherboards I think).After this you can turn on the computer enter BIOS setup by pressing Del key during booting and re-enter the data.
RAMIf Windows starts up like I said above and a blue screen shows up and restarts there must be a problem with your RAM. So turn of the computer and remove the RAM. The computer will not work without the RAM. So clean it and connect it back properly. If these are difficult for you to understand you better get your system to a repairing centre.
If you find your hardware is working properly and the problem persists go to “How to Fix Windows Start up Failure”. Suggestions or for any help on doubts, you can leave a comment.