Let's see...built my first PC in 1991, was running off Windows 3.1.
Basically, was a Windows user until 2005, when someone gave me an old copy of Red Hat to play with in 2004. All my hardware was not detected (especially the wireless card), when back to Windows in less than an hour.
Stayed with Windows until Ubuntu 6.10 and 7.04 came out, played around with it and again went back to Windows after an hour because of undetected graphics and wireless card.
Stayed with Windows again until Linus released v.2.6.27 of the kernel, which, for the first time, supported by wireless card. Think that was roughly around 2007 - 2008. (Fantastic, it took whole 4 years for my ancient wireless card to be supported. Thank god there was Windows XP and Vista to breathe life into my hardware during those years).
Stayed with v 2.6.27 of the kernel ever since then, even up till now. First distro that ran on the 2.6.27 kernel was Ubuntu, then later switched over to Debian Lenny for a period of time in 2009 until finally settling on RPM-based distributions. Desktop is now running a quad boot of Windows Vista x64 (primary OS), OpenSUSE 11.1 x64 with custom 2.6.27-59 kernel, Fedora 10 x64 and Mandriva Free 2009 (32-bit).
Guess I can say i have a lot of 'first' distributions, although it does not change the fact that I still end up using Windows Vista more than half the time.
'First' distro that introduced me to Linux: Red Hat
'First' distro that actually worked: Ubuntu
'First' RPM-based distro that worked: Mandriva One 2009 , subsequently Mandriva Free 2009
'First' RPM-based distro that was used seriously: Fedora 10
'First' RPM-based distro which required a custom kernel to compile a specific WiFi driver: OpenSUSE 11.1 with custom 2.6.27-59 kernel
I was first exposed to Ret Hat in 1999 or 2000, but the first distro that I installed on my own computer was Mandrake Linux.
[Off topic: Then I tried SUSE, then OpenSUSE, then Ubuntu. I stopped using Windows completely once Ubuntu 7.10 was released and I have been using Ubuntu (and Kubuntu, and UbuntuStudio) ever since then. I have tried about 10 other distributions in VirtualBox, but none have convinced me to migrate away from the Debian / Ubuntu family.]
My first contact with Linux was on a VPS that was running CentOS. I followed a guide to get a simple LAMP set up, only because I was learning PHP at the time and I wanted to know how web servers worked.
After that I got the itch to try out the much fabled Ubuntu on a VM. Suffice to say, after a couple of days, I began to see just how superior the platform was in many ways to Windows. Then began my months of distro-hopping and getting to grips with the bash shell.
Now I'm on Arch Linux, and I'm pretty sure I've found a permanent home now. It's only been a year or so since my initial contact with Linux, but I'm just amazed how much you get to learn when you use an OS that doesn't treat you like a brainless lump of meat. *glares at windows*
I have a dual boot running though, because I need Windows to play the latest games.
Redhat 5.2 for me. It even came with a paperback installation manual.
I missed out on 5.2. I bought Redhat 5.0 and was all excited to run it, I installed it and it didn't work for me. So I turned it into the first embedded Linux, I took the CD out of my machine and threw it so hard it stuck into my wall! At one time Redhat X.0 releases were renowned for stinking. 5.0 was no exception. I didn't give RedHat another serious try until 7.1 after that. I ran 6.2 briefly, just install it, check it out, then get rid of it sort of a thing. There was nothing terribly wrong with 6.2, but nothing so compelling about it that I wanted to keep on using it either.
Slackware ("for 386 and 486 PCs") back in 1994 - it came on a magazine cover CD and I was hooked. I dual-booted with Windows NT and later Windows 2000, with Linux gradually becoming the dominant OS, until about 2001, when I finally nuked my Windows partition. (I think it might have been when my video capture card started working under Linux.)
Slackware gradually morphed into a homebrew distro using essentially the same very-minimal package format with rewritten package management, automated build-from-source, ultra-fast init scripts, various experimental modifications and an ARM port along the way in about 2001/2 which I ran on an Acorn RiscPC (mainly for fun), until pressure of work meant I could no longer keep up with maintaining it, in about 2007.
At that point, I switched to Gentoo, for its customisation capabilities, and have been using that ever since on my home and work PCs and servers.
I started with the 0.99 kernel with SLS. Slackware was the first distribution I ran full time. I evaluated Red Hat and its derivatives along with SuSE and others -- I have a couple of distributions I run at work, but I still run Slackware at home.
My first Linux distro was Red Hat 5.2 (Apollo). At the time, though, Windows 95 was my primary OS; Linux was just something I played with. There wasn't a lot that I could do with it. CD's worked some of the time. It took me forever to figure out how to change the resolution. Eventually, I got my modem to work. By the time Ubuntu Dapper came around, Linux was a lot more user friendly, so I ditched Windows.