Transfering files to PC halves the bytes?

The file size of the show on your PC should be roughly the same size as it is on the Tivo, UNLESS you are using TivoDesktop Plus to automatically convert the show for a portable device.

If you are only using the free version of Desktop, have you checked the file on your computer? Did the show download in its entirety?

Are you using anti-virus software on your computer? Some anti-virus software programs limit the size of file transfers.

Also, make sure the hard drives on your computer are formatted as NTFS. A hard drive formatted in FAT-32 has a file transfer limit of 4GB.

I recorded a few 30 minute shows.

On Tivo, they are arround 990 MB.
On PC they are like 440-ish MB.

They are 30 minutes on WMP.

There is one 1 hour show that's like 2.4 / 1.3 MB respectively.