C++ compile Error E166

Hi,

I am just started to learn C++ programming and was wondering if anyone could please help with the following error from the codes that follows:

Error:

v24.cpp(164): Error! E166: col(17) cannot convert right pointer to type of left operand

From:

if (port == COM1)
{
oldintv = _dos_getvect(0x0C); <- Error on this line?
_dos_setvect(0x0C, newintvcom1);
outp(0x0021, (intenable & 0xEF));
}


I am using Open Watcom C/C++ compiler and this is the error message:

"The C++ language will not allow the implicit conversion of unrelated class pointers. An explicit cast is required:
Example:
class C1;
class C2;
void fun( C1* pc1, C2* pc2 )
{
pc2 = pc1;
}"

The source code is (i think) 16-bit and therefore I am using the win16-bit settings on the Watcom to compile the code.

Any advice and help is much appreciated, thanks

Best Regards
Casey