I cannot get into Windows on my Mac HELP!

My imac27 has win 7 and used to access it via bootcamp, I installed parallels to be able to use both at the same time but I got tired of paying them everytime mac had an update to continue using it.

My daughter updated the mac os oneday without me knowing, i was purposely not doing it knowing once i did i wouldn't be able to get back into windows without paying parallels again, so once she did that I just decided to remove the program from the mac completely.

This is where the trouble began, I don't mind using bootcamp method, but I can't get into windows at all now even!

This is what happens now as I reboot I hold option key to choose the windows bootcamp type startup, I see the windows drive, choose it and i get a brief microsoft bar along the bottom then a very quick flash of a bluescreen then it goes blank and i am at my mac sign in screen.

The windows install is nothing huge but there is one program i use often and I just need access to it to do a project for work, I'd love to just be able to boot back into windows like the old days but I have no idea what to try or do to fix this, any help or suggestions greatly appreciated.

I do have my original windows 7 install disc and serial and a cdr disc I had to make originally that I named windows drivers for bootcamp install, but I have no idea what steps to try to get this working again, certainly appreciate any help and direction on what to try.

I tried installing the windows 7 disc and rebooting via option key chose windows it loaded a recovery option completed, yet upon reboot same thing starts blue screens and goes back to mac sign in, tried it again this time restoring to a previous version of windows successfully yet upon rebooting same thing, so it must be something broken on the mac side allowing windows to load after removing parallels, i asked in parallels forums months ago no help figured I would try here...

It sounds like the Windows 7 boot sector has become corrupt. Trying to repair Windows on a Mac that's setup for Boot Camp and dual booting is a waste of time as it usually never works. Your best bet is to get into the Boot Camp assistant, tell it to remove the Windows partition and restore it to OS X. After that is completed, try installing Windows 7 again using Boot Camp. A clean install should get you back to where you can dual boot to Windows as before.

Note that you will lose all your Windows data if you do the above. And we strongly recommend that you make a backup of your Mac OS X system prior to doing anything.

I have win 10 on a external SSD running on my iMac and it works flawlessly no bootcamp as I had problems with it and no virtual it is quite easy to do and should work with win 7 just google it.
Dell