If you are not familiar with these things, ATI Radeon 4100 and ATI Radeon 4200 are video processing units that can be placed in netbooks. The 4200 is considered to be the newer version between the two. The same company which is ATI both produces them.
The 4200 can support DirectX 10.1 and will also have the UDV2 video recorder. The clock speed of the 4100 is known to be shorter as compared to the 4200. It will also not have the same power as the 4200. Take note that there are now more advanced chipsets that are available aside from these two. Always check the chipset before you purchase any netbook.
It can be confusing to know the differences between the different specs of laptops and computers when you are not too familiar with the terms that are usually used. These two are known to be integrated graphics or shared memories for notebooks. These are the two latest video processing units, but they have some differences. The 4100 is slower than the 4200.
There are also some features that are available in the 4200 that are not available in the 4100. It is best that you know the various technical details so that you can decide which one you should get between the two. Some of the differences may not be too obvious for the type of work that you plan to do.