Compilation Error

[scool]

hello

we have install on our windows 2008 server .net 3.5 sp1 & mvc2
we have migrate our website to this newly installed server.

the problem is that after all the successful installations our website keeps displaying that error
copy paste from event viewer application log

3007
A compilation error has occurred.
12/24/2011 1:22:14 AM
12/24/2011 12:22:14 AM
595aea3710484db8bc06b2c5b24812d9
3
1
0
/LM/W3SVC/7/ROOT-15-129691597344152472
Full
/
C:\Inetpub\vhosts\domain.gr\httpdocs\


3216
w3wp.exe
PATRASEVENTS\IWAM_plesk(default)
HttpCompileException
c:\inetpub\vhosts\domain.gr\httpdocs\Web.config(131): error CS0234: The type or namespace name 'Linq' does not exist in the namespace 'System' (are you missing an assembly reference?)
http://one4all-radio.de/infusions/g...mtitle.php?titlelink=http://85.25.84.227:9800
/infusions/gr_radiostatus_panel/streamtitle.php
79.226.73.94

False

PATRASEVENTS\IWAM_plesk(default)
16
PATRASEVENTS\IWAM_plesk(default)
False
at System.Web.Compilation.AssemblyBuilder.Compile() at System.Web.Compilation.BuildProvidersCompiler.PerformBuild() at System.Web.Compilation.ApplicationBuildProvider.GetGlobalAsaxBuildResult(Boolean isPrecompiledApp) at System.Web.Compilation.BuildManager.CompileGlobalAsax() at System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled() at System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters)



the error message on website is

Compilation Error
Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS0234: The type or namespace name 'Linq' does not exist in the namespace 'System' (are you missing an assembly reference?)

Source Error:

Line 129: <add namespace="System.Web.Mvc.Html" />
Line 130: <add namespace="System.Web.Routing" />
Line 131: <add namespace="System.Linq" />
Line 132: <add namespace="System.Collections.Generic" />
Line 133: <!-- Microsoft.Web.Mvc is used for asp.net mvc futures that is not yet implemented by core mvc fucntionality located in System.Web.Mvc -->


Source File: c:\inetpub\vhosts\domain.gr\httpdocs\Web.config Line: 131


is it something am i missing? the application pools installed correctly and .net 3.5 is also installed.
any ideas?