mconfig: 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/mconfig - from package: mono-web

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

On Debian possible default full paths are:

/usr/bin/mconfig - from package: mono-devel

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

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