selectivly changing data

Hello,

       I have an sql database that has the has incorrect data in it,  I need to go thru and replace specific data values with correct information,  I've been doing this manually so far but its just taking forever.

Can someone help with a bit of sql code to do the following ?

here is the query that I've been using to get the data that I've been manually changing...
select CPU_UTIL from PERFMON where CPU_UTIL > '100'

this gives me all the data that is incorrect (CPU_UTIL is a percentage value but some systems are screwy and giving a 324653 value I need to change everything that is above 100   to 100.


Thanks for your help!