Limiting 7zip CPU usage on Windows Server 2008 (from batch file)

Don't worry about the actual CPU percentage, instead you should start the process using a different priority. So from the command line you should be able to use start /low command to start a command that only runs the system is IDLE.

If you are working in powershell you can do something like this:

$start = New-Object System.Diagnostics.ProcessStartInfo
$start.Arguments = "--argument1 --argument2"
$start.FileName = "C:\bin\7zip.exe"
$proc = New-Object System.Diagnostics.Process
$proc.PriorityClass = [System.Diagnostics.ProcessPriorityClass]::BelowNormal
$proc.StartInfo = $start
$proc.Start().WaitForExit()