#1: Just FYI and future reference, RAM use of 90% or more is fine. The OS will automatically try and use as much RAM as it possibly can to improve performance rather than just having it sit idle. The slowest RAM is still hundreds of times faster than the fastest SSD, so why not load data into RAM that you are likely going to use while your computer is otherwise sitting idle? This RAM allocation will go up/down based on the need from other programs.
#1.5: You really should think about adding at least a minimum of 1GB more of RAM if running Win 7. I'd personally go for broke and bring the total up to 4GB. No point going past that if you're running the 32-bit version and you could even make an argument for not going past 3GB, so do that if it's significantly cheaper.
#2: It sounds like one of two things happened. Either A) your bootloader has been hosed and all you need to do is use the repair functions of Windows 7 to restore it (use google for specifics) or B) your boot drive is hosed and you're looking at anything from formatting and reinstalling Windows to replacing the drive entirely.
I was importing pictures to my ssd from a camera and watching youtube and for some reason my ram usage was at 90+% so I turn my computer off. When I turn it back on it says "An operating system wasn't found. Try disconnecting any drives that don't contain an operating system." After seeing this I just try restarting it thinking it was some sort of random thing, but it still says it. I then disconnect my camera and unplug the cables from my secondary HDD and it still does the same. I've tried unplugging it, unplugging the cables from both drives and I have no clues as to why it won't work. When I go into the bios it doesn't even show my ssd.. I've also made sure all the cables are plugged in. If anybody has any ideas as to why this is happening or what I can do to troubleshoot it, please help! Thanks a lot (: