Hi Missys_Garden,
You may refer the following link and try the methods provided and chek if it helps:
Error message when you try to add or remove a program on a computer that is running Windows XP or Windows Server 2003: "The Windows Installer service could not be accessed"
http://support.microsoft.com/kb/315346
Hope this information is helpful.
Praseetha K
Microsoft Answers Support Engineer
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