Today, a 1977 $25 United States Savings Bond Series E would be worth $128.45-138.04 depending on what month it was issued. Also, since the bond was issued in 1977, it has matured and is no longer earning interest so you might as well cash it in.
You can find the exact value (depending on what series and month in 1977 it was issued) using the US Treasury website savings bond calculator:
http://www.treasurydirect.gov/BC/SBCPrice

