Ram avail @ startup used tb 38% now 42%?

[Grey Aliens]

I am new to PPC and have learned tons from you guys, Thanks.
If I am reading correctly, the program manager displays available memory. the more apps i open, the smaller this number gets. get it, but I used to always have 38% and now with everything closed it is 42%. the only difference is the hack I did to the phone to enable tethering. With all programs closed, why would it be at 42% and what do your phones run at? and laslty, where can I check to make sure there is nothing running in the background / or to make sure there is no memory leak?

so if you can all post where you are at..
I, HTC TOUCH SPRINT with no extra software running at startup (that I am aware of).
42%.

After shutdown and restart 29%. (that is new to me! first time I paid attention to memory avail right after a reboot..) thanks for your help.