Use Microsoft Installer (MSI and MSP files)

Slipstream
It is a best practice when creating slipstreamed installations to create an administrative install path, then slipstream the patches (MSP files) into the installation. Administrative installations are deployments of install files that can be referenced later to perform a scripted (or standard) installation.

Code:
msiexec /a "D:\setup.msi" 
* Define a admin install point at prompts such as as "\\filesrv\ArcGIS Desktop"

Code:
msiexec /a "D:\setup.msi" /p "D:\ArcGISDesktop10sp2.msp" 
* Define a admin install point at prompts such as as "\\filesrv\ArcGIS Desktop"

Code:
msiexec /i "\\filesrv\setup.msi" /qb

Batching (When Slipstream Fails)
The following code is for a batch file that performs a batched installation of ArcGIS Server and then patches the server with the latest service pack:

Code:
#ServerDeployment.bat
msiexec /i \\metro\released\10_Final\ArcGIS_Server_NET_GISServices\English\Setup.msi /qb
msiexec /p \\metro\released\Service_Packs\10.0\SP2\English\ArcGIS\ArcGISServerGISServices10sp2.msp /qb

Forcefully Removing Programs
Virtually any software can be forcefully removed from a Windows OS by following these steps:

Warning:
The above procedure should only be used as an absolute last resort when all else fails. Whereever possible it is always advisable to attempt to repair, uninstall, or re-install the product because forcefully wiping the program will almost certainly lead to orphaned registry entries, libraries, and engine files on the system.

User Data & Profiles
The following document from Microsoft discusses Windows User and Program Data profiles from Windows XP to Windows Vista/7. This is a good read for anyone that has questions about how Windows profile folders behave and how to manage them from an IT perspective: Managing Roaming User Data Deployment Guide.

For details on the ArcGIS User Profile see: ArcGIS_Desktop#ArcGIS_User_Profile