pc-compare: 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 Debian possible default full paths are:

/usr/bin/pc-compare - from package: probcons-extra

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

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