I wanted to reply with full code, but I am missing the ASPI drivers and ... I am not going to mess with it :-).

A couple of observations:

1) You have already "told" "Win32::API" that your argument is a pointer (LP prefix) to a struct/record, hence you should just pass the perl scalar and not a reference to it. In other words, use this

"$x = GetCdRomDrives($cds);" 
instead of 
"$x = GetCdRomDrives(\$cds);"
[download]

2) If I understand the documentation correctly you must call the "$x = GetCdRomDrives($cds)" once and then loop through the results:

foreach $TCdRom (@{$cds->{TCdRom}}){
    printf("%s \n", $TCdRom->{HaId};
    ...
    ...
}
[download]

Of course I cannot check the code and expect some syntax issues/errors :-) YMMV.

CptSkripto