How To: Fix "The format of specified network name is invalid" error when mapping a SharePoint site

Symptoms

• You receive the error message "The format of specified network name is invalid"
• You are trying to map a SharePoint or IIS site as a network drive
• You have verified with nslookup the server name is resolvable

Resolution

• Check that "WebClient" service is Enabled and set to start Automatically. 

References

Microsoft TechNet (WebClient (System Services for the Windows Server 2003 Family and Windows XP Operating Systems)