When overclocking you need to already have the os and everything else installed, running stable, tested and fine, all on STOCK settings. If you started to overclock before you installed your os, then there is a possibility your os and everything else installed may not be stable, especially with you saying your gettings hangs and reboots. So, if this the case you will need to reinstall everything from scratch.
But, if you installed, tested stable on stock settings, then your fine. You shouldnt have any problems with your os, however, sometimes the hangs, reboots and especially if you got BSOD's, may damage or corrupt files. To test, run stress tests for your overclock, like prime 95 for atleast 8 hours. If it passes your oc is fine and so is your os, but you may still have problems in the future. Unfortunately i dont know of any way to be 100% certain that your os wasnt damaged during oc error's, so short answer, reinstall os now, rather then later.
With any overclock, there is always the possibility that your oc may crash the os in the future, but its very rare and its like asking how long your cpu will work, when overclocked compared to stock.