In your comment, you ask if you can do it with Notepad++. Yes, you can! Notepad++ supports the use of regular expressions for find and replace.
Here is the regular expression that will match the strings you want:
refreshrate="\d{1,3}"
\d{1,3}
means "1 to 3 digits". So this regular expression will match
refreshrate="45"
,
refreshrate="100"
, etc. In the Replace field, put
refreshrate="60"
.