By starting with well configured distros from the start like Ubuntu is a good idea. When you are reinstalling distros it means you are looking for a pill to solve your problems. You need to learn how to configure your computer. Embrace it
Sometimes, even the best distros will come up short and then you will have to learn to modify or alter settings to work with your setup. I don't know what the status is with the ati x1400 from a brief mention I saw on the net (albeit some time ago) it was not
yet working well. There may be a fix on the actual ati website that hasn't found it's way into Ubuntu repositories (if that is indeed your problem). In that case you will need to install it manually (maybe even having to deinstall the drivers installed by default).
Narrowing down what's not working, researching a fix and doing it one problem at a time is the recommended solution. Sometimes, other distros will have helpful advice (in the past Gentoo had all the answers in the forums). You might want to save important info on a flash disk while mucking around (this period may last years

) Remember it's meant to be fun and don't worry about breaking something.
I don't want to sound like an ******* but as always with GNU/Linux, it's best to work out hardware compatibity before buying; that is the power we have as consumers. I always play safe when buying computer hardware by waiting a generation before jumping in.
Distro hopping doesn't work and only delays learning about configuring your computer.