cp.dll: 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/lib64/mp/bin/cp.dll - from package: mp
/usr/lib/mp/bin/cp.dll - from package: mp

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

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