The simplest way if you have little or no customization of the "sharepoint 2.0" (next time say WSS 2.0 or SPS 2003 so we know exactly where we are - I'm assuming WSS 2.0) system is to upgrade in place to WSS 3.0. Take a backup first so you can go back if the upgrade in place fails.
Once that is done save the calendar with Save List as Template (with content).
This *v3* template can then be used in any v3 site.
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If you have a lot of customization in your present installation and can find suitable media install WSS 2.0 on a spare server (needs little RAM) and then run Save List as template (with content) on the original server.
This *v2* template can then be used on your spare server.
Then upgrade the spare server in n place to WSS 3.0.
As before save the calendar with Save List as Template (with content).
This *v3* template can then be used in any v3 site.
FAQ sites: (SP 2010)
http://wssv4faq.mindsharp.com; (v3)
http://wssv3faq.mindsharp.com and (WSS 2.0)
http://wssv2faq.mindsharp.com Complete Book Lists (incl. foreign language) on each site.