aniki:
Has this problem just started, or is this a system you are just now putting together? Also, did you buy the Duron and the AZ11 new, or have they been used before? Regardless, here are some things to check:
1. There is an onboard jumper- "CLR_CMOS" (around battery) for the user to clear CMOS data. It should be placed on pins 1-2 (normal) and not 2-3 (clear). Also, it's possible that your CPU is unable to boot up with the specific settings now in your Bios -- therefore, definitely try clearing your CMOS using this same jumper, that is, setting it at 2-3 (clear) and then returning it to 1-2 (normal);
2. Make sure the jumper for switching between 100/133MHz is set to 100MHz(it's the jumper close to the secondary IDE connector). My guess would be that this is your problem. FIC states that the maximum the AZ11 can accept is a CPU FSB at 100Mhz (which is true for all KT133 chipsets, so don't feel as if there is something "wrong" with your AZ11 because of this) and Memory subsystem (BIOS SDRAM timing as "Host +33"

at 133Mhz;
3. Finally (and this is a long long LONG longshot), if you bought the Duron used, make sure that the L6 bridges are connected for a 7x multiplier. You can check by matching your L6 settings on the top of your CPU to this chart
here. Your Duron 700 L6 settings should match the 700 settings found in the first column of this chart (again, this is a longshot, and MAY only be problem if you bought the Duron used, and your cooling system -- heatsink, fan, etc. -- is less able to overclock the chip than that of its former owner);
Good luck!!!