Okay I am going to be pretty concise here. The laptop specified here is a fairly decent machine which if upgraded to 4GB would perform better however do check if you are using a 32-bit OS since they have to be patched to support RAM of capacity of 4 or more Gigs. Now moving ahead, T4200 is a fairly reasonable CPU for performing day-to-day operations however the cache is 1MB which definitely doesn't set it in competition with it's other family members such as CoreDuo or Core2Duo that have L2 cache size of 2 or greater capacity. Answering your questions:
1- It should not overheat lest you try to operate your notebook in a room temperature exceeding the limits defined and you to be even more careful, use a laptop cooling tray while working for the heat channel to dissipate heat properly.
2- 4500M is a standard on-board graphic controller which would give you a reasonable good performance especially if you are trying to watch a movie or play a game (even offline) that doesn't have much of graphics requirement. In case you want to play heavy games such as Quake, Resident Evil, etc that do require a good GPU, you would definitely require a machine with an nVidia or an ATI GPU to give you a good performance while handling graphic engine processing effectively.
3- With current configurations as I said earlier, it is a fairly decent performer for day-to-day activities such as internet browsing, documentation and media such as playing movies and songs however if you want it to be used as a proper gaming console i.e. Gamer's PC ... I would be fairly honest and say no. Not even with RAM upgrade, it can't beat the gaming PCs. In fact if you really want to do online gaming, I'd strongly suggest that you opt for a desktop with a processor such as Core2Extreme or Core i7/Extreme with an external GPU, which would definitely raise the cost however give you the performance that you need.
I hope it helped. For any further questions or queries, feel free to contact us.
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