You don't have to do anything with Sync Center, I don't even know what it does. It was just a reference to help locate the System tab.
However, I believe your problem is the 32 bit version of Windows 7. There is a version called 64 bit that allows 64 bit programs to run. The 32 bit version of Java is limited to around 1 gig of memory and the 64 bit version has a limit that computers won't be reaching within the next 50 years because its very high.
Your computer has 4 gigs of memory, so I would suggest installing a 64 bit OS. The 32 bit version of Windows 7 is also limited to recognizing around 3.5 gigs of memory as usable.
If you installed a 64 bit OS, not only would an extra 0.5 gigs of memory be usable, there are small performance advantages and you could give the FTB launcher 2 gigs of memory for best performance in the game.
If you don't want to reinstall your OS, there are 2 options, the first is called dual booting. For example:
http://www.ubuntu.com/download/desktop/install-ubuntu-with-windows
You could then install Java on the Ubuntu OS and play FTB there. This requires a larger amount of technical inclination, so I suggest installing Windows 8 or Windows 7. In terms of difficulty, Ubuntu is probably the most user friendly Linux operating system.
The second option is lowering graphical settings like particles and view distance, this should reduce memory usage.
Let me know if there is anything you don't understand or need help with.