We have already posted about a freeware utility which lets you clear the most recent file list called MRU Blaster, but just in case if you want to clean or delete the list of the all searches you made through windows search, you can use the following mentioned below.
MRU Search Cleanup Tool helps you clean the recent search entries, this tool works with windows 7 and also backward compatible, it is also portable in nature runs directly with its executable so no need to install it.
Or if you want to get rid of windows search recent search suggestions, then you can permanently disable the recent search suggestions by following the procedure below.
Procedure To Permanently Disable Recent Search Entries In Windows 7
1. Click Start, type ‘gpedit.msc’ in search box and open it.
2. Navigate to User Configuration > Administrative Templates > Windows Components > Windows Explorer
3. Look for “Turn off display of recent search entries in the Windows Explorer search box” entry in the settings panel under Windows Explorer.
4. Click ‘Enabled’, Apply and Ok. Logoff to let the changes take effect.
[ Source WebTrickz ]