The HP
Pavilion 6535 computer was shipped only with the 466MHz Celeron.
The faster Celerons you are noticing are provided with the newer 6635
and 6735
models.
As they also use Socket-370
(PPGA) flavour Celerons, you should be able to swap the stock
processor for a faster one. You should not have to change any of the BIOS
settings, as the motherboard should recognise the faster chip
automatically. An upgrade to the latest BIOS is a good idea, though, to
ensure you have the latest compatibility fixes and Windows
2000 support.
If you are ready to go for a 700MHz
Celeron, you should be able boost your CPU speed by
at least 60%