I don't think that there is anything wrong with Vista, as such, I use it every day and I don't find I've had any problems with it.
Windows Vista comes with a built in tool that can tell you about the computer it is running on, you should see if your computer gets a good score rating in this tool.
Click on the Start Orb (menu) and then click on Control Panel.
From the Control Panel, click System and Maintenance.
Underneath System (third one down), click on the "Check your computers Windows Experience Index base score" link.
The Windows Experience Index is a new feature of Windows which rates the computer you are using for its ability to run Windows Vista. The base score is the one you need to look at, but there are ratings for each category also.
My base score is 4.5.
If you look at new Vista software, you should notice that it mentions what the base score of your computer should be to run that software.
You might buy a game that requires a base score of 3 to run. If you computer has a base score of 2, that game will probably run very slowly.
If you are unhappy with the product you have purchased, consider taking it back to the point of sale, the shop or web site you bought in from. Remember your rights as a consumer and say that you are unhappy with the product. Perhaps you can swap it for something else.
I hope that I have answered your question fully. Please rate my answer if you find it useful.