Don't add a terminating null character in RtlCopyString, if the destination buffer isn't large enough. 
A ansi/unicode string doesn't need a terminating null character.

Modified: trunk/reactos/lib/rtl/unicode.c

--- trunk/reactos/lib/rtl/unicode.c	2005-01-13 20:30:59 UTC (rev 13029)
+++ trunk/reactos/lib/rtl/unicode.c	2005-01-13 20:53:35 UTC (rev 13030)
@@ -2195,11 +2195,14 @@

       return;
    }
 

-   copylen = min (DestinationString->MaximumLength - sizeof(CHAR),

+   copylen = min (DestinationString->MaximumLength,

                   SourceString->Length);
 
    memcpy(DestinationString->Buffer, SourceString->Buffer, copylen);

-   DestinationString->Buffer[copylen] = 0;

+   if (DestinationString->MaximumLength >= copylen + sizeof(CHAR))
+   {
+      DestinationString->Buffer[copylen] = 0;
+   }

    DestinationString->Length = copylen;
 }
 
@@ -2222,10 +2225,13 @@

       return;
    }
 

-   copylen = min (DestinationString->MaximumLength - sizeof(WCHAR),

+   copylen = min (DestinationString->MaximumLength,

                   SourceString->Length);
    memcpy(DestinationString->Buffer, SourceString->Buffer, copylen);

-   DestinationString->Buffer[copylen / sizeof(WCHAR)] = 0;

+   if (DestinationString->MaximumLength >= copylen + sizeof(WCHAR))
+   {
+     DestinationString->Buffer[copylen / sizeof(WCHAR)] = 0;
+   }

    DestinationString->Length = copylen;
 }