$tempFile="pstips.net"
$fs=New-Object System.IO.FileStream($tempFile,[System.IO.FileMode]::OpenOrCreate)
$fs.Seek(2GB,[System.IO.SeekOrigin]::Begin)
$fs.WriteByte(0)
$fs.Close()

#生成完畢后，還可以檢驗下
(Get-Item $tempFile).Length/1gb
<#
 # 輸出為：
 # 2.00000000093132
#>