Mine is Windows Vista. I know after this reply most of the people would think what kind of a person is this who likes Vista. Well, I should tell you this is the OS which I have been using for quite some time now and feel comfortable with. And believe me I have even done development work using this OS and it has never betrayed me. Though there are some small issues but the OS is great even for hardcore software development.
98Lite is my all time favourite. I still have XP SP2 running nearly every day on my second "in use" PC. As for modern OSs, I'm surprisingly happy with Windows 7 64 on my main desktop. And.... as far as other OSs that use "windows" ... I have very fond memories of GEM/TOS on the Atari. I used TOS up until the late 90s.
im using Windows 7 Home Prem, but i love ubuntu, of course customized to get rid of that ugly unity, it just doesnt do what i need at the moment, but if everything was windows 98 compatible, trust me i would go right back to that, but then xp is kinda nice also
Windows 7 is by far my favorite so far, and I can already tell win 8 will suck As for the older ones...XP is actually pretty good
As per to my reply two posts ago! Windows 7 is an Amazing OS, i want to change to Ubuntu or something, now that ive seen the direction Windows is heading.. Problem is, i have all my computers synced together, so anything i do on one computer, automaticaly syncs with all my other computers/laptops so im not sure i can really be bothered to wipe all the Operating Systems, and re install everything, and set up the sync again...