Windows 7 - windows 7 64bit ram

my acer aspire as8730-6918 has 4gb ram installed changed from win 32bit to 64bit to use all 4 still has 2.93gb available is there anything i can do whats holding me back do i need more ram installed

Since the aspire is a laptop model it is possible the memory is marked 'shared' meaning it's split between the system and the graphics card.
If this is the case, the setting to reduce resources to the graphics is more than likely in the laptop's bios.

Your motherboard only supports so much memory wether it`s 32 or 64 bit. Your video card is using the rest. Adding more ram will not change anything. As long as all the ram shows up in computer properties, your fine.

I have quite a few 64 bit computers showing 4 gigs, but only 2.93 usable, 3.5 usable etc.

That model supports up to 4 GB according to Acer,

Acer Support: Aspire 8730 Series Specifications

The chipset in it on the other hand supports up to 8 GB,

Mobile Intel® GM45 Express Chipset

Unfortunately it also requires the memory remap feature in the bios to be enabled to use the full 4 GB. Whether that seeing is there or not is entirely up to Acer. If it is there enabling it will make the full 4 GB minus whatever is allocated for the video card. If it isn't there Acer has either hidden it and set it to disabled or not included it at all, of which there is nothing you can do.