For this edition of my Power User tips for PowerShell, I’m going to share my (heavily annotated) prompt function. Feel free to to copy useful pieces or just place the whole thing in your profile script 
I’m not going to say anything more, I’ll let the comments speak for themselves.
Edit: Someone just pointed out that I forgot the bit of my prompt that sets my current path into the window title, and I realized I also forgot the bit that puts (Admin) in the title if you’re running “elevated” on Vista.
[new] Edit: Ok, how many people noticed that I incorrectly used the Environement.CurrentDirectory when I set the WindowTitle (meaning it would only work right in FileSystem drives)? Fixed now.
# Set-Prompt.ps1 (Dot-Source from your profile)
###################################################
# This should go OUTSIDE the prompt function, it doesn't need re-evaluation
# We're going to calculate a prefix for the window title
# Our basic title is "PoSh - C:\Your\Path\Here" showing the current path
if(!$global:WindowTitlePrefix) {
# But if you're running "elevated" on vista, we want to show that ...
if( ([System.Environment]::OSVersion.Version.Major -gt 5) -and ( # Vista and ...
new-object Security.Principal.WindowsPrincipal (
[Security.Principal.WindowsIdentity]::GetCurrent()) # current user is admin
).IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator) )
{
$global:WindowTitlePrefix = "PoSh (ADMIN)"
} else {
$global:WindowTitlePrefix = "PoSh"
}
}
function prompt {
# FIRST, make a note if there was an error in the previous command
$err = !$?
# Make sure Windows and .Net know where we are (they can only handle the FileSystem)
[Environment]::CurrentDirectory = (Get-Location -PSProvider FileSystem).ProviderPath
# Also, put the path in the title ... (don't restrict this to the FileSystem
$Host.UI.RawUI.WindowTitle = "{0} - {1} ({2})" -f $global:WindowTitlePrefix,$pwd.Path,$pwd.Provider.Name
# Determine what nesting level we are at (if any)
$Nesting = "$([char]0xB7)" * $NestedPromptLevel
# Generate PUSHD(push-location) Stack level string
$Stack = "+" * (Get-Location -Stack).count
# my New-Script and Get-PerformanceHistory functions use history IDs
# So, put the ID of the command in, so we can get/invoke-history easier
# eg: "r 4" will re-run the command that has [4]: in the prompt
$nextCommandId = (Get-History -count 1).Id + 1
# Output prompt string
# If there's an error, set the prompt foreground to "Red", otherwise, "Yellow"
if($err) { $fg = "Red" } else { $fg = "Yellow" }
# Notice: no angle brackets, makes it easy to paste my buffer to the web
Write-Host "[${Nesting}${nextCommandId}${Stack}]:" -NoNewLine -Fore $fg
return " "
}