Is there a access checker webpart which can be used for 2010???

I've not been able to test it, but I have created a workitem request for this as information on SP2010 should be clearer. Please vote if you agree :)

http://accesschecker.codeplex.com/workitem/7653

I got it to work in Sharepoint 2010 by changinig one line of code.  In SPPermissionsTreeNode.cs the code is calling a shareopoint internal method to get the users persmissoins. The signature of that method change etween 2007 and 2010.  The second parameter used to be of type  ISecurableObject, now its an SPSecurableObject.

If you change luine 242 of SPPermissionsTreeNode cs from

Type[] parameters = new Type[] { typeof(SPUserToken), typeof(ISecurableObject) };

 to

Type[] parameters = new Type[] { typeof(SPUserToken), typeof(SPSecurableObject) };

It works. There is still some issue with the masterpage that i need to workout however (the display is all messed up).

Russell

To fix up the display isues  just change the page  tag on the two aspx pages in the LAYOUTS\AccessChecker folder  to use v4.master :

<%
@ Page language="C#" MasterPageFile="~/_layouts/v4.master" Inherits="Microsoft.SharePoint.WebPartPages.WebPartPage,Microsoft.SharePoint,Version=12.0.0.0,Culture=neutral,PublicKeyToken=71e9bce111e9429c" %>
 
and remove the SPWebPartManager from each of the aspx pages as well. 
 
With these changes, its working great in 2010!

Made the recommended source code changes for SharePoint 2010, ran the build program to create a new setup.exe file, but how might one skip the System Check during setup that checks to see if Windows SharePoint Service 3.0 is installed or not, or change the System Check to look for a SharePoint 2010 installation?

You need to copy the project code to a Sharepoint 2010 box with Visual Studio 2010 installed. Open the project in VS2010 to convert it, Then make the changes and deploy the package.