Basically, there are two options.
1) Upgrade to either Win7 or Win8.
The hardware requirements for Win8 may dictate your choice.
2) Migrate to another Operating System; Linux, BSD, or Macintosh.
I have zero experience with a Mac.
If you are comfortable working with the command line [root console] and compiling programs, then your choices for Linux or BSD are wide open.
For fresh-from-Windows noobs, the best choices for Linux are Mint or Ubuntu. [just my humble opinion]
http://distrowatch.com/
[see the Page Hit Ranking list on the right-hand side of the page for links to each distro's sub-page]
My best recommendation to get away from Windows would be PC-BSD, but it requires a PC with a 64-bit processor. [My 8 year old PC was running the 32-bit version of XP Home Edition, but it turns out that the AMD Sempron it has is really a 64-bit processor.]
http://www.pcbsd.org/en/about/
http://wiki.pcbsd.org/index.php/PC-BSDÂ ... dbook/10.0
Any "Windows-only" programs that you have can be run in Wine.
http://en.wikipedia.org/wiki/Wine_(software)