Consider replacing your battery? (then it went away..)

at school, my laptop was working perfectly until a friend let me borrow a usb to drag a game file onto my computer.

that's when all this started.

the computer started lagging and the OS would freeze temporarily (weird..)
from then on up to a few minutes ago, the processor percentage would go high then low then high then low and etc

and same with the ram, the percentage used would go high and low and in a RAM time graph, you would see a wavy line...

After that, i noticed that my battery said "plugged in, not charging". this happens to me often so i just unplugged the a/c adapter and minutes later, i plugged it back in.

then i encountered the "consider replacing your battery" error for the first time in my life.

to try and fix this problem, i did a system restore (to fix the lagging) and the battery error was still there.

THEN i unplugged it and then it disappeared.. (no more replacing your battery error)

i did a powercfg -energy in an elevated cmd, and it turns out im at 38% of design capacity on my last full charge...

which is weird because on december 12, 2010 (based on last report), i had 88%

can it really drop 50% over a month? and what if the error comes back? does anyone know what it means?

Thanks

update: battery was at 88%, went to charge it; it said 66% - Charging, i unplugged it again and now it dropped to 49% ?!?!

what's weird is
an energy report 2 hours ago reported my battery chemistry was "NiMH" with last full charge at 22k and now it's reporting chemistry as "LION" with 20k
annoying thing;..

i have malwarebytes im goign to try that

i do have both + threatfire
great now malwarebytes just froze.
restarting scan

i tried mse scan and malwarebytes scan.. this is weird a random a battery problem