HDD hard drive with Windows Vista + Ubuntu (partition) removed. Can I now connect it to a laptop with Windows 7 and play it over or use it differently?

HDD hard drive with Windows Vista + Ubuntu (partition) removed. Can I now connect it to a laptop with Windows 7 and play it over or use it differently?

Basically yes, so you can view and use all files in the Vista partition.

You can't read the files in the Ubuntu partition with a standard Windows, this is only possible with a GNU / Linux Distro or with your own program for Windows which can read ext4 partitions (if you have a standard Ubuntu installation without encryption and with ext4 partition)

Problem solved. I simply connected the removed hard drive via USB to the laptop and via F9 into the BIOS, then you are asked where you want to boot from. So then on the external hard drive and Enter. After that the Grub Manager opened as usual and I was able to use xubuntu as well as Windows. All two operating systems and files are there and working, I never thought it would be that easy.

Yes, if your MB can also boot via USB, which all new ones can actually do, they can boot on plates on the USB bus.
However, you should note that depending on the converter, USB can be a lot slower than SATA.