Resource Usage

SYSTEMINFO

You can cheat and use good old SYSTEMINFO from any command line. This will give you fairly comprehensive system information.

systeminfo

Memory Usage

Again you can cheat, use SYSTEMINFO and filter the output:

systeminfo | Select-String 'Memory:'

The code snippet below will work with PowerShell 3.0 and newer

if ([Environment]::Is64BitOperatingSystem) {
  #64 bit logic here
  get-process | Group-Object -Property ProcessName | 
  % {
      [PSCustomObject]@{
          ProcessName = $_.Name
          Mem_MB = [math]::Round(($_.Group|Measure-Object WorkingSet64 -Sum).Sum / 1MB, 0)
          ProcessCount = $_.Count
      }
  } | sort -desc Mem_MB | Select-Object -First 25
} else {
  #32 bit logic here
  get-process | Group-Object -Property ProcessName | 
  % {
      [PSCustomObject]@{
          ProcessName = $_.Name
          Mem_MB = [math]::Round(($_.Group|Measure-Object WorkingSet -Sum).Sum / 1MB, 0)
          ProcessCount = $_.Count
      }
  } | sort -desc Mem_MB | Select-Object -First 25
}

The code below will execute on Windows 7 and newer.

if ((Get-WmiObject win32_operatingsystem | select osarchitecture).osarchitecture -eq "64-bit") {
  #64 bit logic here
  get-process | Group-Object -Property ProcessName | 
  % {
      [PSCustomObject]@{
          ProcessName = $_.Name
          Mem_MB = [math]::Round(($_.Group|Measure-Object WorkingSet64 -Sum).Sum / 1MB, 0)
          ProcessCount = $_.Count
      }
  } | sort -desc Mem_MB | Select-Object -First 25
} else {
  #32 bit logic here
  get-process | Group-Object -Property ProcessName | 
  % {
      [PSCustomObject]@{
          ProcessName = $_.Name
          Mem_MB = [math]::Round(($_.Group|Measure-Object WorkingSet -Sum).Sum / 1MB, 0)
          ProcessCount = $_.Count
      }
  } | sort -desc Mem_MB | Select-Object -First 25
}