How to create an event handler for sharepointmoss 2007

The easiest ways is to download and install WSP Builder from codeplex its a visual studio plug in that adds the correct confirmations, using statements, mapped folder paths, overrideable functions, future scope, etc. for you by right clicking and adding a event to your project you can also us it to build your WSPs, deploy to SP, cycle IIS and attach to the correct w3wp for debugging purposes. If however this is not for you, it is possible to do it 'manually' by following the following instructions.

Add the Microsoft.SharePoint reference and using statement to your newly create project.

Derive your class from SPItemEventReceiver
e.g. public class MyEventAction : SPItemEventReceiver

Override the required *ed or *ing function(s) out of the list required for your project:
ItemAdded
ItemAdding
ItemAttachmentAdded
ItemAttachmentAdding
ItemAttachmentDeleted
ItemAttachmentDeleting
ItemCheckedIn
ItemCheckedOut
ItemCheckingIn
ItemCheckingOut
ItemDeleted
ItemDeleting
ItemFileConverted
ItemFileMoved
ItemFileMoving
ItemUncheckedOut
ItemUncheckingOut
ItemUpdated
ItemUpdating

e.g.

public override void ItemAdded(SPItemEventProperties properties)
{
   base.ItemAdded(properties);
}

Create a folder that syncs to the hive location under templates then features then create a folder with the name of the feature and in it create a xml file called Feature.xml

Update the Feature.xml to look sorting like the following.

<Feature Scope="Web" Title="My Event Handler"
Id="GUID" xmlns="http://schemas.microsoft.com/sharepoint/">
   <ElementManifests>
      <ElementManifest Location="Elements.xml"/>
   </ElementManifests>
</Feature>

Now create an Elements.xml file in the MyEventHandler folder that identifies the assembly, class, and method to implement as the event handler.

<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
   <Receivers ListTemplateId="104">
      <Receiver>
         <Name>MyEventHandler</Name>
         <Type>ItemAdded</Type>
         <SequenceNumber>10000</SequenceNumber>
         <Assembly>MyEventHandler, Version=1.0.0.0, Culture=neutral, PublicKeyToken=a26b5449ac4a4cf3</Assembly>
         <Class>MyEventHandler.AddedAction</Class>
         <Data></Data>
         <Filter></Filter>
      </Receiver>
   </Receivers>
</Elements>

The Type attribute ListTemplateId is for the type of list this action applies to:

ID	Name
100	Generic list
101	Document library
102	Survey
103	Links list
104	Announcements list
105	Contacts list
106	Events list
107	Tasks list
108	Discussion board
109	Picture library
110	Data sources
111	Site template gallery
112	User Information list
113	Web Part gallery
114	List template gallery
115	XML Form library
116	Master pages gallery
117	No-Code Workflows
118	Custom Workflow Process
119	Wiki Page library
120	Custom grid for a list
130	Data Connection library
140	Workflow History
150	Gantt Tasks list
200	Meeting Series list
201	Meeting Agenda list
202	Meeting Attendees list
204	Meeting Decisions list
207	Meeting Objectives list
210	Meeting text box
211	Meeting Things To Bring list
212	Meeting Workspace Pages list
300	Portal Sites list
301	Blog Posts list
302	Blog Comments list
303	Blog Categories list
1100	Issue tracking
1200	Administrator tasks list
2002	Personal document library
2003	Private document library

Save and build project.

Deploy using STSADM.

stsadm -o installfeature -filename MyEventHandler\Feature.xml

stsadm -o activatefeature -filename MyEventHandler\Feature.xml 
-url http://Server/Site/Subsite

Then you will have to do and iisreset using cmd

iisreset -noforce

For more information see:
http://msdn.microsoft.com/en-us/library/ms453149(v=office.12).aspx