The difference (64MB) between the 256MB physical memory and the 192MB reported by Windows is what's reserved for integrated graphics. Integrated graphics use your system resources (primarily RAM) to simulate a real graphics card. The small chip on your motherboard does a fairly good job, especially for the price, but it does take away from your system resoyrces (as you've seen), and can't produce as high-quality graphics as a graphics card. Thus, for optimum results, it's recommended that you purchase a ''true'' graphics card, although it's not needed, especially considering it's a budget/low-end system that's not going to be used for a lot of gaming or multitasking.
As far as the processor registering slower than it's supposed to be, it might just not be running at full speed because it's not needed at the present time. This helps save power (cost of running it) and reduce the amount of heat created (allowing the fans to work less, reducing both cost and noise).
All in all, it sounds like it's running as it should. However, I'd consider watching the flyers for deals on RAM in the near future. It's recommended that you have at least 256MB of RAM to run Windows XP, and 64MB have already been allocated to graphics. Also, with only 40.62MB available with what I'm assuming is just basic programs, you may find yourself out of resources if you try to perform more intensive tasks. I looked at your specs, and if you do choose to upgrade your RAM, look for a single 256MB stick of PC2700 SDRAM, which will double your memory. (Best Buy currently has a stick of K-Byte 256MB PC2700 SDRAM on sale for $30.) Instructions on how to install the RAM are usually included, but I'm sure one of your friends or someone from Best Buy, Circuit City, etc could install it for you.
Hope this helps,
John