You are going to need to get a GFD (Gold Finger Device), a good Heatsink and fan, and your gonna have to remove the plastic case that surrounds the PCB. Your motherboard is fine for overclocking because your not gonna really do anything with it, just leave all the settings as they are and let the GFD do all the work.
If you goto this site:
Overclocking and GFD Basics
It will tell you everything you will need to know on how to overclock your classic athlon. I have used this site many times.
I would buy an Alpha P7125 HS/F it will cost you about $30 for one of the best coolers for your athlon. I have a TD2 GFD which I got at the site listed above.
You can overclock somewhat using your motherboard but you'll have to do it by upping the FSB (front side buss) and the problem with doing it that way is that you basically overclock your whole system, vid card, memory, sound card...as well as the processor and the problem is that many times those peripheral things can't handle that...so you are very limited in how high you go using the FSB....
I've rambled enough...just goto the site and get your self a GFD and you can overclock that 750 probably somewhere up around 900 to 1000 mhz..
Good luck and if you need any help feel free to email or PM me..