Haha, my computer is running just fine. It's perfectly normal. Granted I do have a couple of large apps in memory (Lotus Notes, ugh), but aside from that it's just fine. That's how it's supposed to run just the same as every other modern OS. As a friend of mine said, sometimes people just shouldn't see numbers because a lot of times they don't understand them. A small amount of free memory tells me my machine is efficiently using my RAM and not wasting it. As you can see with the "Available" number, there is a plentiful amount of RAM available to be cleared if something needs it. And the number of cpu cycles it takes to knock something old out of cache is nearly nothing, so no, I don't think it would be noticeably faster if the memory wasn't in use before.
Some services start with Windows just like the services that start at boot on Android. The services that task killers kill, and the services that start themselves right back up after being killed, wasting cpu cycles and battery. If you use a task killer and selectively went through and excluded every service so that you wouldn't have wasteful recycling of those services whenever you killed tasks, it wouldn't be as bad, but it still wouldn't be necessary. Android and Windows are not the same thing. Android, and all other mobile platforms, keep applications in memory after you close them because the UI is nearly always a single window UI. You can't multitask and leave multiple applications open like you can on a PC. It's the equivalent of minimizing an app on Windows, however, mobile apps are specifically built to save their state if necessary and be ready to be killed whenever memory is needed.
Well I've been running and repairing windows machines for years and years and the only time I see 99% RAM use is either when they have a malware infection or a shed load of high RAM use programs/games open
What is using all of your RAM? Look in processes and click the RAM column to move highest to top