If your available free hard drive space is steadily decreasing, despite efforts to clean up your mail box, temporary internet files, browser download folder and Windows Update folder – check your local Sharepoint installation (use something like WinDirStat to get a full overview of where your space has gone, or check directly in the folder where your SQL database files are stored (e.g. C:Program FilesMicrosoft Office Servers14.0DataMSSQL10.SHAREPOINTMSSQLDATA)).
Over time, the log databases will get really big unless you reconfigure this yourself. I recently deleted the .log file for my content database, but now only a week later the 4GB I released were reduced to nothing again. This time it was the .log file for the Config database. Open SQL Server Management Studio, right click the database in question, choose Task –> Shrink –> Files. This will give you the properties for the database, but because the default file shown will be the .mdf you have to pick “Log” from the File type drop down list:
Ensure “Release unused space” is selected and reclaim the missing GB.