qt3to4: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/qt3to4 - from package: qt-devel
/usr/lib64/qt4/bin/qt3to4 - from package: qt-devel
/usr/lib/qt4/bin/qt3to4 - from package: qt-devel

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/lib/x86_64-linux-gnu/qt4/bin/qt3to4 - from package: libqt4-dev-bin

You may install the required package with command apt-get install {package}

Error in other languages:
qt3to4: bevel nie gevind nie
qt3to4: comandă negăsită
qt3to4: comando não encontrado
qt3to4: commande introuvable
qt3to4: command not found
qt3to4: käsku ei ole
qt3to4: không tìm thấy lệnh
qt3to4: komanda nerasta
qt3to4: Kommando nicht gefunden.
qt3to4: kommandot finns inte
qt3to4: komut yok
qt3to4: nie znaleziono polecenia
qt3to4: níor aimsíodh an t-ordú
qt3to4: no se encontró la orden
qt3to4: no s'ha trobat l'ordre
qt3to4: opdracht niet gevonden
qt3to4: parancs nem található
qt3to4: perintah tidak ditemukan
qt3to4: príkaz nenájdený
qt3to4: příkaz nenalezen
qt3to4: команда не найдена
qt3to4: командата не е открита
qt3to4: 命令找不到
qt3to4: コマンドが見つかりません