Linker Error

Dear Experts,

I am getting a linker error in VC7.

I have written a singleton

//SysInfoFileManager.h

namespace SysInfo
{
    class SysInfoFileManager
    {
        SysInfoFileManager(){}
        SysInfoFileManager(const SysInfoFileManager&);
        ~SysInfoFileManager(){}
        SysInfoFileManager& operator=(const SysInfoFileManager&);
        static SysInfoFileManager* _pinstance;
    public:
        static SysInfoFileManager* instance();
        //void trim(std::string& str);
    };
}

SysInfo::SysInfoFileManager* SysInfo::SysInfoFileManager::_pinstance =
0;

//SysInfoFileManager.cpp

#include "SysInfoFileManager.h"

namespace SysInfo
{
    SysInfoFileManager* SysInfoFileManager::instance()
    {
        if (!_pinstance)
        {
            //Lock Mutex
            if (!_pinstance)
            {
                static SysInfoFileManager sysInfoFileManager;
                _pinstance = &sysInfoFileManager;
            }
        }
        return _pinstance;
    }
}

I am getting follwing error. Any suggestion would of great help.

Error 1 error LNK2005: "private: static class
SysInfo::SysInfoFileManager *
SysInfo::SysInfoFileManager::_pinstance" (?
_pinstance@SysInfoFileManager@SysInfo@@$$Q0PAV12@A) already defined in
SyinfoWebServerClass.obj SysInfoFileManager.obj

Error 2 fatal error LNK1169: one or more multiply defined symbols
found C:\Webserver\SyinfoWebServer\Debug\SyinfoWebServer.dll 1

Thanks
siddhu