Just some Overcloking reference numbers just change you multiplier if its not

These are the various setting on my Asus board
The example CPU is a Celeron 366 chosen because it and the Celeeron 300A are the most overclockable CPUs due to their multipiers of 4.5* 66=300 simply clock from 66MHZ to 100Mhz to get 450 (103 yeild 464MHZ
and the 366 5.5*66=363, 5.5 *100 yeilds 550

5.5*66= 363.5 PCI Bus=33.4
5.5*75= 412.5 PCI Bus=37.5
5.5*83= 458.15 PCI Bus=41.65
5.5*100.3= 551.65 PCI Bus=33.43 This is where yours is at
5.5*103=566.5 PCI Bus=34.33 Possible with PC 100 mem
5.5*105=577.5 PCI Bus=35.0 Possible with PC 100 mem
5.5*110=605.0 PCI Bus=36.67
5.5*112=616.0 PCI Bus=37.33
5.5*115=632.5 PCI Bus=38.33
5.5*120=660.0 PCI Bus=40.00
5.5*124=682.0 PCI Bus=31.0
5.5*124=682.0 PCI Bus=41.3
5.5*133=731.5 PCI Bus=33.3 PC 133 Memory
5.5*133=731.5 PCI Bus=44.33 (not good)
5.5 *140=770 PCI Bus=35.0
5.5*150=850 PCI Bus= 37.5

Overclocking FSB settings 66MHz -133MHz
I've got 2 Celeron 300a's running at 4.5*103=464 the
PCI bus speed is at 34.33 So I have a little experience in this area.
most problems with OCing are due to overclocking the PCI bus as you can see below using the 75MHZ and the 83 MHZ really jumps up the PCI bus speed. You may have better luck going up to 100MHz FSB. Notice the PCI bus speed is almost the same as is is at the defauls 66MHz.
If that don't work bump up your voltage 1 setting at a time and see if it'll come around. I wouldn't go over 2.2 volts though. Also remeber not all Celeron are created equal.
Keep in mind that for stability you want to keep the PCI bus speed as close as possible to the default of 33.4MHZ or your stressing all your PCI devices