winpopup-install: 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/winpopup-install - from package: kdenetwork

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

On Debian possible default full paths are:

/usr/bin/winpopup-install - from package: kopete

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

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