Can you boot up into the advanced boot options, usually by tapping F8 as you switch on, but this key/combo can be different depending on the make & model of computer.
I think it is still F8 for an Emachine.
Select Repair your computer > change/confirm keyboard input language > Next > change/confirm username and enter password if one used > Next
In the Recovery Environment (RE) there is a Startup Repair option although that doesn't always work, but try that first.
If it reports it is unable to auto repair, select Command Prompt and while the Startup Repair will have already done this, manually enter these commands -
bootrec /fixmbr
bootrec /rebuildbcd
exit
Then Restart to see if it boots up.
If it doesn't, go back to the Command Prompt in the RE and enter -
bcdedit |find "osdevice"
chkdsk x: /r
Where x=the partition letter as it doesn't always see the volume in C:
That is a Pipe symbol before find and is the uppercase of \
Make a note of what it reports and if it finds any KBs in bad sectors.
Enter c: and at the c: prompt enter sfc /scannow to see what that reports.
That will either report no integrity violations - found corruption and repaired files or it was unable to repair all files.
If it's the latter then that will need a different resolution - but see how you get on with those steps.
