Hi Folks, Sorry about this - wonder if anyone might be able to help me?

I have an existing v6 site that I need to upgrade, re-theme etc. I've installed it using SQL Express and WebMatrix but I'm getting the yellow screen on death! I'm stumped on how to fix it - this is the first time I've tried to install an existing site locally. Below I've included the message, I'm sure it's something stupid that I've done.

Thanks in advance. Darren

Server Error in '/' Application.

The system cannot find the file specified Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ComponentModel.Win32Exception: The system cannot find the file specified

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[Win32Exception (0x80004005): The system cannot find the file specified]

[SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)] System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) +347 System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) +78 System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) +191 System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1 retry, DbConnectionOptions userOptions) +154 System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource1 retry, DbConnectionOptions userOptions) +21 System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource1 retry) +90 System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource1 retry) +166 System.Data.SqlClient.SqlConnection.Open() +96 Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteReader(String connectionString, CommandType commandType, String commandText, SqlParameter[] commandParameters) +60 umbraco.DataLayer.SqlHelpers.SqlServer.SqlServerHelper.ExecuteReader(String commandText, SqlParameter[] parameters) +37 umbraco.DataLayer.SqlHelper`1.ExecuteReader(String commandText, IParameter[] parameters) +84

[SqlHelperException: Umbraco Exception (DataLayer): SQL helper exception in ExecuteReader] umbraco.DataLayer.SqlHelper1.ExecuteReader(String commandText, IParameter[] parameters) +246 umbraco.cms.businesslogic.web.Domain.<GetDomains>b__0() +77 Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, CacheItemPriority priority, CacheItemRemovedCallback refreshAction, CacheDependency cacheDependency, Nullable1 timeout, Func1 getCacheItem, Object syncLock) +141 Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, CacheItemPriority priority, CacheItemRemovedCallback refreshAction, CacheDependency cacheDependency, Nullable1 timeout, Func1 getCacheItem) +116 Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, CacheItemPriority priority, CacheItemRemovedCallback refreshAction, Nullable1 timeout, Func1 getCacheItem) +97 Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, CacheItemRemovedCallback refreshAction, Nullable1 timeout, Func1 getCacheItem) +94 Umbraco.Core.Cache.HttpRuntimeCacheProvider.GetCacheItem(String cacheKey, Nullable1 timeout, Func1 getCacheItem) +91 Umbraco.Core.CacheHelper.GetCacheItem(String cacheKey, TimeSpan timeout, Func1 getCacheItem) +253 umbraco.cms.businesslogic.web.Domain.GetDomains(Boolean includeWildcards) +151 Umbraco.Web.Routing.PublishedContentRequestEngine.FindDomain() +223 Umbraco.Web.Routing.PublishedContentRequestEngine.PrepareRequest() +16 Umbraco.Web.UmbracoModule.ProcessRequest(HttpContextBase httpContext) +316 Umbraco.Web.UmbracoModule.

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.6.106.0