"Donald B" wrote...
I have tons of times in this format:
:42:01
:02:58
:04:45
:25:13

and need to change to:

0:42:01
0:02:58
0:04:45
0:25:13

Are these numbers formatted as ":mm:ss"? If so, change the number format to
"[h]:mm:ss". If they're text, and you want to leave them text, use

="0"&x

where x is the address of a cell containing one of these times. If they're
text and you want to convert them to values, use the formula

=--("0"&x)

and format appropriately.