How old is your iPod? Unless your iPod is one of the Late 2006 upgraded 30GB or 80GB iPods, you don't have the search function. The original version cannot be updated to the specification of the later version such as longer battery life, search function or brighter screen. On the earlier version there is a the quick scroll feature which kicks in when you are scrolling fairly rapidly through your list and shows the letter of the alphabet you are at.
You can see the search feature here:
iPod (late 2006) features
You can distinguish the Fifth Generation iPod (Late 2006) from the original Fifth Generation iPod by the last three digits of the serial number. V9K, V9P, V9M, V9R, V9L, V9N, V9Q, V9S, WU9, WUA, WUB, WUC, and X3N. The Fifth Generation U2 Special Edition iPod (30 GB Late 2006) serial number's last three digits are W9G:
Identifying different iPod models