When overclocking the 1st success is if it's able to POST. Then boot OS. Then stress test. If it fails any of this, the OC is unsuccessful. Then it depends on the hardware if you can tweak some settings - mostly Vcore and memory/cache timings. Some can do it in BIOS or other software and the other only with hardware mods.
You can always buy a tested 100Mhz part - but there is still no guarantee it will work fine with your motherboard as this is a factor too. At least I had different successes with non-Vcore moded PODP5V83 - some wouldn't be stable at 100MHz with one motherboard but would be with the other.