The second Tuesday of each month is known as "Patch Tuesday" - it's when Microsoft release the majority of the scheduled patches for it's operating systems, such as Windows 7, Windows 8, etc.
Sometimes - as others have said - this can mean that you computer takes a long time to start. This months update was *immense*. For example, many Windows 7 systems got anywhere from 50 to 75 updates to run through.
Sometimes updates do cause problems with your machine.
Regardless, even if it is an update issue your machine should still:
1) get past the BIOS boot screen (usually a black screen that flashes up in the first couple of seconds from pressing the power button).
2) You should still be able to boot it into Safe Mode or at least access the Windows boot option screen.
(usually you tap F8 during the boot sequence to access this, but some vendors such as HP change the key....so maybe google for "<your computer manufacturer> windows boot screen key" or similar.
If it's not getting that far then it's likely to be something else such as:
1) Boot record corruption (rare, unless you've been fiddling or the drive is on the way out)
2) Hard disk is on its way out - again, fairly rare and usually there are warning sounds/signs, unless it's an SSD which will 'stop dead', but your BIOS would complain about not being able to see the disk.
3) Hardware failure, such as a RAM issue.
Cheers,