mstconfig: 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/mstconfig - from package: mstflint

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

On Debian possible default full paths are:

/usr/bin/mstconfig - from package: mstflint

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

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