Yes, it does mean your program is a 32 bit version running.
All programs included inside GNS3 doesn't support 64 bits, for instance, the dynamips is running in 32 bits (this is totally normal and have no consequence).
This should have no impact for the idle-pc (at least it didn't have any on my computer).
I would recommend to :
1st stop every router, and check your CPU is at 0 or very low, if it isn't you should correct that problem prior to running any thing under GNS3,
2nd run only one router, do the idle-pc, and try different settings until finding the correct one.
If you still have the idle-pc not working with only one router, you should try another image, perhaps their is a problem with your 3700 image (which one are you using so I can test ? ).
Your proc and RAM are pretty good, their shouldn't be any limitation there.