Where has my disk space gone?
Here are the top consumers of disk space and what you can do about it:
1.) After extraction, Windows 7 itself can take over 5GB for a clean installation, and upwards of 10GB if it is a pre-installed copy from the manufacturer. This is normal.
2.) If you are upgrading from a previous version or installing another copy of Windows on the same partition, look for a WINDOWS.OLD folder in the local drive. (Usually C:\) That will contain previously-installed programs, documents, etc. that had to be moved for the installation. Copy out what you need/want and delete the rest.
3.) System Restore can reserve a considerable amount of space (up to 15% of the drives capacity) for saving restore points, particularly if your copy of Windows 7 supports Shadow Copies. Unlike with XP, there is no easy slider option to adjust the maximum space used, but you can still do so using the command line. To do so, press Windows + R and type in cmd followed by pressing Enter.) When the command prompt appears, type in the following, entering the correct drive letters and intended size: vssadmin resize shadowstorage /for=C: /on=C: /maxsize=5GB (This is just an example - be sure you enter the desired drive letter and maximum size you desire.)
4.) IBM and Lenovo include a feature called Rescue and Recovery, which automatically backs up key files similarly to System Restore. While this is designed to protect you from data loss it can take up considerable space on your hard drive, in excess of 50GB in some cases. If this proves to be problematic you can disable the feature by accessing the ThinkVantage Rescue and Recovery utility and unchecking the "Schedule Your Backups" box under Set Schedule and Preferences. You can then recover the lost space by going into the Advanced preferences and using the "Delete Backups" option. A special thanks to Cnet member rimb1172 for bringing this issue to our attention.
5.) The Recycle Bin can take up space as well, so right-click it, select Properties, and adjust the permitted capacity as needed.
6.) The system paging file (also known as Virtual Memory or the swap file) also takes up space on the hard disk, though it is recommended that you let Windows continue to manage it as it sees fit. Restricting it can reduce system performance and cause virtual memory error messages.
7.) A lesser-known fact is that there are two different definitions of the terms megabyte, gigabyte, etc. In short, hard drive manufacturers say 1GB is equal to 10^9 bytes, whereas Windows is based on the idea that 1GB equals 2^30 bytes (technically a gibibyte, not a gigabyte). Thus, a 100GB hard drive will be reported as being 93GB by Windows. You were not cheated, its simply a difference in definition.
8.) Last, but certainly not least, personal files, downloads, etc. can take up hundreds of GBs. To identify the areas in which most of the space is being used I suggest the free program TreeSize. With a few clicks you should be able to find the source, and delete it if you desire.