What ECS mobo is it? There are several, all with different options in the BIOS.
But, I should warn you, ECS motherboards generally have very few options for overclocking. They do not allow for much variation in front side bus selection... they will have a couple of set options.
And on top of that, the Celeron 1.7 is a very poor overclocker. If your ECS board only has bus speeds of 100 and 133, don't expect to do any overclocking, because that 1.7 will almost definitely not make it on a 133 bus, which would be 2.2ghz.
So, in short, let us know what model your motherboard is and we'll see what we can do.
edit: I just looked in the Overclockers.com CPU database and found there are only 4 entries for Celeron 1.7... anyway, it seems that those that did overclock were not able to do so without changing the core voltage. If your BIOS will let you change the core voltage, you may be in luck.