Have you upgraded to WordPress, since I believe that b2 isn’t being supported any more?
Here are some references that will help you upgrade and change your “skin” to a WordPress Theme. Many people have not only kept the same look on their site, they’ve actually improved it.
http://codex.wordpress.org/Upgrade_1.2_to_1.5
http://www.tamba2.org.uk/wordpress/upgrade/upgrade_en.html
http://codex.wordpress.org/
Support board for people still using b2, though it’s all unofficial, you really should be using wordpress or b2evo instead etc. etc.
I have already upgraded to WordPress & I want to use the skins I made for my site before installing WordPress; the ones that worked when I had just b2.
If you have WP 1.5.x you have to transform them into themes.
See Themes and Templates > http://codex.wordpress.org/Blog_Design_and_Layout
So in otherwords, I have to use WP themes for my blog?
Nevermind then.
If you replace all the b2 tags with equivalent wordpress ones it should be ok.
“So in otherwords, I have to use WP themes for my blog?”
No.
Though it’s not difficult to convert one’s pre-1.5 templates to a theme (in your case, *really* pre), you don’t have to. You just need an include for wp-blog-header.php (to WP-ize your template), and follow IanD’s advice.
Most WP tags are virtually identical to b2 ones anyway, so you shouldn’t have a problem. You don’t have to use the theme system at all if you don’t want to, but keep index.php in the root directory as you did with b2.
The ‘loop’ and (as Kafkaesqui mentioned) the call to blog-header.php in the very first line of your template will need to be updated to the WP versions, but other than that you need to change very little.