Before you get started, check whether you have the correct hardware and system requirements.

• Processor 766 MHz (preferably 1.5 GHz)
• RAM 256 MB (preferably 512 MB)
• Hard Disk space 1.5 GB on system drive 4.5 GB on installation drive
• Operating System Windows 2000 (Professional)

In order to use VSTO, the following software and components must be installed on your computer:

• MS Visual Studio .NET (2003+; or Standard 2003+; build 3077+). Do this before installing MS Office!
• MS Office Professional 2003+ edition (or just MS Office Excel 2003+). You do need more than a Standard installation; best is a Full installation, or at least the following components:
• Make sure Service Pack 1 (SP1) is included. Otherwise, download it from microsoft.com.
• Install also VBA and the .NET programmability support. The latter will put the Primary Interop Assemblies (PIAs) on your machine (in the Windows Global Assembly Cache, or GAC, created by the .NET Framework) — with the option "Run From My Computer". Make sure you have PIAs for at least Excel, MSForms, and Graph. These PIAs are the "connection" between VS.NET and your Office applications.
• Finally, install VSTO as the crowning glory. The Team Suite CD is minimal, but sufficient.
• You may also want to also install MS SQL Server or MS SQL Server Desktop Engine (MSDE 7.0+ or 2000+) if you need to connect Excel to an SQL server for database purposes. MSDE is included with your Office 2003 CD.
• One more caveat: Your monitor should not be set to High Contrast. To fix this: Control Panel → Accessibility Options → Display → Use High Contrast. If you do have to change the Contrast setting, you must run the setup for VSTO again.

After this installation, you will find new additional choices in the New Project dialog box of Visual Studio 2003+: There is a new node called MS Office System projects. Pick your favorite language — probably VB.NET — and start a VSTO Excel project, after you have decided on the question as to whether you wish to create a companion document or to attach this assembly to an existing Excel document.

People who want to use your .dll files newly created in VSTO on their own computers are called End Users. What should be installed on their computers?

• MS .NET Framework version 2.0+ (before installing Office 2003+).
• VSTO runtime (a mini version of VSTO).
• MS Office Professional 2003+ (or at least MS Office Excel 2003+), including the necessary Primary Interop Assemblies (PIAs).
• Make sure Office 2003+ Service Pack (SP1) was also included. If not, you can still download it from microsoft.com.