Stop what you're doing and back up any data from the system to an external drive.
Try to do a system restore. (Microsoft Support)
Then follow online instructions for startup repair. And automatic system repair. (howtogeek link)
If those do not work, delve into the event logs and look for something to explain why your system is going into safe mode. Also check the device manager for errors and warnings. When searching the net for answers to the things you find, try to prioritize places like TechNet.microsoft.com and support.microsoft.com, then stack exchange, then blogs.microsoft.com then other sites. Answers.microsoft.com CAN have some good info, but the people delivering answers there are volunteers not paid experts.
If you do need a full reinstall, you will need to gather drivers, software installers, and other files. You'll want to use a second computer to download these. Be sure to keep all these files in one place. Make yourself a document that explains what each file is for and where you got it. Once you're up and running, put all those things on a thumb drive or DVD so that next time you need to refresh, you have everything ready to go.