|Your best bet is to install Kernel EX compatibility program. (This allows many Windows XP programs to run on Windows 98/ME.)|
Then install Firefox 3.6.28 and Flash Player 9,0,47 (9.0.47).
Flash Player 10 will also work with Kernel EX but you have to download Adobe's archived file which is >100MB. Flash 9 still works on YouTube and is a smaller file.
This should keep you current enough until you're ready to upgrade your computer or OS.