Boot error on startup

Greetings,

I am a first time PC builder. After assembling and installing Windows 7, occasionally I would have a boot error on start up, Windows wouldn't boot because of "recent hardware or software changes". The times it won't boot, my 250 gig ssd won't be appearing in bios. Other times, it would boot fine. I realised my SATA port of the SSD was 6. I changed it to port 1 which was working with my hdd for storage. Now it won't boot or read my ssd at all. Do you think this is a faulty ssd or am I doing something wrong? What's weird is that if it doesn't show in bios and I have a boot error, I can boot from Windows 7 disk, and attempt to install Windows on my ssd. I tried to reinstall Windows on the ssd (on the same partition because I couldn't figure out how to partiton a drive from the ssd on a boot disk) and it wouldn't boot from the start. I have a

250 gig samsung 850 evo ssd.

Mobo: Asus z97a 3.1
Processor: Intel i7 processor
Graphics: Msi gtx 960 4g
HDD: WD blue 1tb

Thank you for any help