Unit shuts down after cpu fan install

Ok, so I had the genius idea of trying to install a new fan in my old system to maybe get away with overclocking to avoid upgrading. I have a decent tech experience, I've built machines in the past and do all of my own upgrades.

Long story short, I ended up scrapping the new fan idea (too big for the tower case) and replaced the old fan. I turn the unit on and it starts up normally, then while its starting windows ( I saw my icons for a couple seconds) it shuts down. I tried this again and it didn't even get past the windows splash screen.

My guess is that the CPU is overheating and that I have messed up installing the fan. I followed all steps, thermal compound, attach to mobo, plug in to mobo, but I may have something loose.

I guess my question: is there anything else that this can be? The power supply seems fine, I know my main Hard drive is working because it did boot. Possibly memory, but that should all be fine. Lastly, my visuals were fine, so I don't suspect a graphics card problem.

Didn't mean to write a book, just figure the more info the better. Thank you all who take the time to read this and double thanks for any additional information that you can give me.

 

Ok, I should really follow my own advice before posting.

I have removed the fan, replaced the thermal compound, and reconnected the fan. Sure enough, next boot has been good for 10 minutes. I'm going to let my computer run for a while, but I think that this problem is solved.