MacBook 13 (middle 2010), 4gb memory, 2.4 Ghz, Intel Core 2 Duo, 300 Gb hard drive After I worked some time on cleaning the hard drive, getting rid of old files and unneeded applications my Macbook suddenly started to make steady hissing noise, seemingly fan noise, doesn't go to sleep when I close the lid. At the same time keyboard doesn't light anymore. Noise starts immediately after pressing the power button and doesn't seem to depend on the temperature, the Macbook stays reasonably cold, a little wormer on the left side. The number of applications opened or closed doesn't influence it in any way. Noise seem to come from the area where the keyboard meats the lid. I've read tons of discussions and articles on the Internet, tried almost all that was advised, including resetting SMC and NVRAM and now just asking for help. Otherwise the book works OK, actually faster than before the cleaning.