Win 7 Ultimate 64bit

Windows XP Professional I got along better. - Maybe I think in some places still too complicated; because everyone says that the handling / operation of Windows 7 is easier than in previous versions of Windows.

One drawback: The automatic Windows Update has the driver software for the numeric coprocessor my slightly outdated mainboards not found automatically and installed; but maintains that the installation of drivers for the coprocessor was not necessary. - I had to install a third-party, the me then three unwanted programs with installed software (driver search-and INSTALLING software). The latter I had to manually uninstall.

For my taste, there are not enough 64-bit software. - 32-bit applications (especially a free anti-virus program) slows down the system considerably.

Nevertheless, I have deliberately chosen the more expensive Ultimate version, because I just wanted to have everything included and my Windows system did not want to build gradually by piece together.

Ultimately, I am very satisfied. Much is simply controlled through automatic updates of itself.