I'm on windows and when the new 1.3 update came it converted my world and it

was running smoothly. The next few days I could not connect to
minecraft.net so I played offline. Then my computer decided to do an
intro of whiteness so I turned it off. I turned it on and I when I tried
to play my save file wasn't there. I checked my .minecraft folder and I
was so so so so relieved to see my file was still there. I tried
logging in again but I was baffled when
it wasn't showing up on the launcher. I tried deleting and redownloading
minecraft and putting my world into the saves file, changing the
level.dat_old to level(2).dat since I already have a level.dat, and
creating new worlds but replacing the new contents with the contents of
my old world. Nothing is working for me and I'm in a rage because I've
spent hours on that world. Does anyone have a
solution?