vreg_latex2html: 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/vreg_latex2html - from package: perl-SystemC-Vregs

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

Error in other languages:
vreg_latex2html: bevel nie gevind nie
vreg_latex2html: comandă negăsită
vreg_latex2html: comando não encontrado
vreg_latex2html: commande introuvable
vreg_latex2html: command not found
vreg_latex2html: käsku ei ole
vreg_latex2html: không tìm thấy lệnh
vreg_latex2html: komanda nerasta
vreg_latex2html: Kommando nicht gefunden.
vreg_latex2html: kommandot finns inte
vreg_latex2html: komut yok
vreg_latex2html: nie znaleziono polecenia
vreg_latex2html: níor aimsíodh an t-ordú
vreg_latex2html: no se encontró la orden
vreg_latex2html: no s'ha trobat l'ordre
vreg_latex2html: opdracht niet gevonden
vreg_latex2html: parancs nem található
vreg_latex2html: perintah tidak ditemukan
vreg_latex2html: príkaz nenájdený
vreg_latex2html: příkaz nenalezen
vreg_latex2html: команда не найдена
vreg_latex2html: командата не е открита
vreg_latex2html: 命令找不到
vreg_latex2html: コマンドが見つかりません