Unfortunately, not every overclock attempt will be a successful one. There are many things which can make a overclocking attempt a failure. You also have to remember that some processors just won't overclock if they were part of a poor batch or stepping. Thankfully, this is unlikely as most processors can at least make the next FSB jump whatever that may be. Thanks to the Intel BX chipset bus design it is very hard to determine which specific piece of hardware or device is not allowing you to overclock properly. This is because the Northbridge and Southbrige chipsets are interconnected, if you like, and when you change one setting you are also, indirectly, changing another. So, basically when you overclock the FSB you are also changing the AGP / PCI and ISA buses - some of these devices don't like to be overclocked and will result in your system not booting or crashing.
As I've said various times before in this guide (like just before), when you overclock your processor you are also overclocking the AGP and PCI slots. Some AGP cards will not work over 66MHz and some PCI devices will not work over 33MHz. So, you will have to allow for this factor when overclocking. Herein lies another option which can be changed on most motherboards, 1/2 or 1/3 divider. What this does is change the MHz of your AGP and PCI bus by 1/2 or 1/3 of the system FSB. Which, in turn makes the devices which don't work when overclocked, work - usually. The fastest setting is 1/2, but it is generally the most unstable setting. If your system fails to boot when overclocked, try setting the divider to 1/3. If the certain device doesn't work when overclocked you may have to consider removing the part or buying another product which can handle the overclocked speeds which you are using.
It could also be that your ram is well, crap (couldn't have said it better myself Junkz). If you buy cheap, unbranded memory you will pay the price with not being able to overclock it much or in some cases not at all.
Or... Your system could already be running too hot and because of this your processor rejects the overclock attempt. Get some more case fans baby! This is just a small list of some hitches which can make it hard for you to overclock.
In this section I have complied a list of motherboard which are popular for Intel FSB overclocking and when using these motherboards you should have no hassles attempting to change the FSB. Despite weather or not you have a slot1 or socket370 processor you can use any motherboard listed below with a slot1 to socket370 adapter (aka riser) card such as the ABIT SlotKET III...
ABIT BX133 RAID
Does it appear we are biased towards ABIT and ASUS, well I guess you could say we are. And we can be, because, in my opinion I think both companies make some of the best motherboards I have ever seen and most overclockable. All of the above motherboards are top choices for Intel FSB overclocking!