If a 100MB makes a difference to you then your hard drive is too small or has way to much stuff on it. Time to clean up.
Start with temporary internet files:
In Internet Explorer, click on Tools / Internet Options.
Under Temporary Internet Files (commonly called TIF), click on Delete Files.
Check the "Delete all offline content" box and click OK
Next, reduce the amount of space allocated to System Restore. It defaults to 12% of the drive which is way to much. Set it so you get as close to 500MB as possible. Some folks here recommend 300MB, so your choice. To change it:
Start / Settings / Control Panel.
Double click on System.
Click on the Restore tab.
Select C: then click the Settings button. Move the slider to reduce the amount, can make a big difference.
Reduce the size of the recycle bin. The default setting is 10% of the drive which is way too much.
Right click on Recycle Bin and select Properties.
Move the slider from 10% down to 2% or so. Click on C: to see how much space that will allocate. Set to 1% if it's still more than 150MB.
Click apply and OK to exit.
If you ever delete anything bigger than the defined size, you'll get a notice that it's too big to fit and do you want to delete it anyway? Just click yes and it's gone, permanently.
To see what is using space on your hard drive, install a program called SequoiaView. Gives you a great visual picture of what is using up drive space. Get it here: http://www.win.tue.nl/sequoiaview/
. Before running SequoiaView, you should make all files and extensions visible. Do this by:
Control Panel / Folder Options / View Tab.
Select Show hidden files and folders
Uncheck Hide extensions for known file types
Uncheck Hide protected opeating system files [Recommended]
Also, in SequoiaView, click on View
and check Enable color scheme
. Makes the displayed data much easier to read.