When you get this error in Windows XP make sure you have given ASPNET user sufficient rights on your physical application folder, it mainly requires read permission.

When you get this error in Windows 2003 server you can right click your virtual directory – permission – grant aspnet user sufficient rights there.

If the above solution doesn’t work here is another alternative,

You could try editing the Machine.config (located in
C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\CONFI G\).

Look for a key userName=”machine”. If you set it to “SYSTEM”
instead the aspnet_wp.exe runs with a different user (with
higher privileges).

Hope this helps

To define a MIME type for a specific extension, follow these steps:

1. Open the IIS Microsoft Management Console (MMC), right-click the local computer name, and then click Properties.
2. Click MIME Types.
3. Click New.
4. In the Extension box, type the file name extension that you want (for example, .pdb).
5. In the MIME Type box, type application/octet-stream.
6. Apply the new settings. Note that you must restart the World Wide Web Publishing Service or wait for the worker process to recycle for the changes to take effect. In this example, IIS now serves files with the .pdb extension.

All you need to install Sharepoint, WSS or MOSS, on Vista is

• You must select the Advanced option during install.
• If you want to run on SQLExpress, manually install it first.  Get it here.
• You have to manually enable IIS7 with the proper options. Web Management Tools and World Wide Web Services. Enable at least the following options in IIS.

Download Vista Helper file from here, and run the setup file WssVista.msi.

Sharepoint on Vista

You will see an UAC prompt select Continue to proceed with the installation.

Once the install has completed you will find the SetupLauncher.exe in the install location you selected. If you didn’t change the default option you will see it under the directory ..\Program Files\WssOnVista\

Sharepoint on Vista

Before starting the setup make sure you have enabled IIS with the following options, Web Management Tools and World Wide Web Services. Enable at least the following options and choose OK.

To set this Go to Control Panel and click Programs. Under Program and Features click Turn Windows features on or off.

Sharepoint on Vista

After completing the above steps it’s time for the interesting part. Locate SetupLauncher.exe and start it. You will once again see an UAC prompt, select Continue.

Sharepoint on Vista

After the SetupLauncher run, select the WSS installation file Sharepoint.exe, or the MOSS installation file, and click OK.  First, the package will be extracted.

Sharepoint on Vista

After the files have been extracted the WSS setup program will be started.

Sharepoint on Vista

The current version only supports the advanced installation option so select that one.

Sit back and relax while SharePoint is being installed, you are running Vista remember

Once installed you can configure your Sharepoint setup.

Sharepoint on Vista

Let the Configuration Wizard do it’s work.

Sharepoint on Vista

The final result is WSS running on Vista, Enjoy!

Sharepoint on Vista

Resource:

Bamboo Solutions

You can find more on their forums. Enjoy!!!