Skracanie stringa

HKEY hkSoftware;
HKEY hkTest;
LONG result;
string buf;
DWORD dwBufSize = 255;
DWORD dwRegsz = REG_SZ;
int a;

result = RegOpenKeyEx( HKEY_CURRENT_USER, "SOFTWARE", 0, KEY_ALL_ACCESS, & hkSoftware );
if( result == ERROR_SUCCESS ) {
        result = RegOpenKeyEx( hkSoftware, "SAMP", 0, KEY_ALL_ACCESS, & hkTest );
        if( result == ERROR_SUCCESS ) {
                result = RegQueryValueEx(hkTest, "gta_sa_exe", NULL, & dwRegsz,( LPBYTE ) buf.c_str(), & dwBufSize );
                if( result == ERROR_SUCCESS ) {
                       sciezka=buf;
                       sciezka.resize(sciezka.size()- 10); //Tutaj wywala mi error podczas działania programu...
                       MessageBox(NULL,sciezka.c_str(),"TEST",MB_ICONINFORMATION);
                       RegCloseKey(hkTest);
                       RegCloseKey(hkSoftware);
                }
          }
} 

result = RegQueryValueEx(hkTest, "gta_sa_exe", NULL, & dwRegsz,( LPBYTE ) buf.c_str(), & dwBufSize );

string str;
char *buf; // albo wchar_t jeśli unicode
result = RegQueryValueEx(blabla, buf, blabla);
str = buf;