Windows XP SP3 (released April 2008) was the final major service pack for Windows XP. It included all previous updates, security patches, and stability improvements. Crucially, on Windows XP. If you are running XP SP2 or earlier, you must first upgrade to SP3 before attempting to install .NET 3.5.
As of 2026, are available. Known vulnerabilities include:
Look for Version string – it should show 3.5.30729.01 or higher. Windows XP SP3 (released April 2008) was the
dotnetfx35setup.exe (web bootstrapper) or dotnetfx35.exe (full offline). The offline version is safer for machines without internet.
: This is the most comprehensive version for XP. If you are running XP SP2 or earlier,
Both can coexist. However, applications targeting .NET 3.5 may be forced to run under .NET 4.x’s CLR, causing compatibility issues. Disable this via <supportedRuntime> in app config.
dir %windir%\Microsoft.NET\Framework\v3.5 dotnetfx35setup
To ensure a successful installation, your system should meet these minimums: