You save an alloc and free that way

Yes - I think that's a better approach.
(However, specifying a return type of char * and then returning an SV * is something that doesn't work well for me ;-)
I find the following works as expected (without any need to dynamically allocate/free memory) , and doesn't throw any warnings:

SV * get_proc_name( int processID )
{
    char szProcessName[MAX_PATH] = {0};

    HANDLE hProcess = OpenProcess
                     ( PROCESS_QUERY_INFORMATION |
                     PROCESS_VM_READ,
                     FALSE, processID );


    if (NULL != hProcess )
    {
        HMODULE hMod;
        DWORD cbNeeded;

        if ( EnumProcessModules( hProcess, &hMod, sizeof(hMod), &cbNee
+ded) )
        {
            GetModuleBaseName( hProcess, hMod, szProcessName, MAX_PATH
+ - 1);
        }
        else {
            szProcessName[0] = '#';
            szProcessName[1] = 0;
        }
    }
    else {
       szProcessName[0] = '*';
       szProcessName[1] = 0;
    }

    CloseHandle( hProcess );
    return newSVpv(szProcessName, 0);
}
[download]

Cheers,
Rob