It depends a lot on what you mean by "easily" :-)

Current upgrade script only starts from releases 1.3 and later. So you must first upgrade to 1.3. Here are 2 very old forum topics that describe the procedure:

- [Forum, topic 333] How to upgrade from version 1.1 to 1.2 ?, WARNING: here come refreshed links for release 1.2.1 and for upgrade1.1to1.2.zip
- [Forum, topic 1240] Release 1.3, WARNING : hre comes refreshed links for release 1.3.4 and for upgrade1.2to1.3.zip

I'm glad I make serious backup of my personal computer because the files hosted on website had vanished!

One you have upgraded to 1.3, follow the upgrade guide to upgrade fro 1.3.4 to 2.0.0.

Let us know if you've succeeded in your 7 years upgrade (1.1 was released on July 19th, 2002)

So I created manually (using the .sql of the install) :
- The column forbidden_categories  in users
- The table user_category
- The column uppercats  in categories
There were still some failures. I had to go in to the admin and do some refresh (Admin > Categories > Editer)

I keep you updated on the following steps ....

Well done.

Maybe you can subscribe (Register) to the forum.
Therefore it will be easier to help you on any questions about new tables or warning messages you could have.