Here is a tool that you can use to do a find and replace on tag markers to,
for example, html. It is designed to convert Wordperfect to x but apparently
works the other way around too.
Of course you could do the same thing with a decent text editor like Vim.
If there are images you will need to convert them to an appropriate format.
Alternatively there is this. It converts Ventura to rtf then do whatever you
want with it.
Alan Litchfield MBus (Hons), MNZCS
PO Box 1941, Auckland