As to the 3GB issue that is not a flaw but a limitation on the OS and hardware design. It's been there since before 2000 so there's been plenty of documentation.
-> Try crucial.com for your next ram.
I have a Toshiba Satellite A135-S4467, it runs Vista Home Premium 32, has Core 2 Duo 1.6GHz processors, and uses the Mobile Intel 945GM Express chipset. It originally came with two 512MB PC4200 DDR2 Ram Modules, which I recently decided to upgrade. According to Toshiba & the compatability specs on the package, the PC5300's can be used when upgrading, which were what I could find readily at hand to upgrade my laptop to its max capacity of 4GB.
The first two boots I was having a hard time figuring out why System settings was only showing 3GB of Ram. After going through some forum posts I saw the 'flaw' in the Vista design which can only use 3GB of expanded memory, and only Vista64, which can work with 8GB (7GB expanded), so even though I felt a little cheated there, I figured my system would still run much better than before. (By the way, if there is a way around this I would appreciate any tips)
After a few more boots of my system however, my system fails to fully start up. I turn on my laptop, the LED power button light turns on, I can hear a disk start up, not sure if it might be the DVD or the hard drive, but my screen does not turn on (it's not just black, its as if the laptop were still off). Everything else is pretty much unresponsive. The keyboard I know isn't working at that point, since I have the settings set up to make my system to shut down when I hut the power button. I have to do the 3sec press on it to shut it down. I don't hear any error beeps either. I already checked my device manager for any possible conflicts, but nothing shows up. I have all drivers up to date.
In the past year I haven't had anything like this happen before, so could it be due to bad ram modules? or what else could it possibly be? As for the installation of the modules, I used appropriate handling techniques when installing them to prevent any static discharge.