where is 'windows picture and fax viewer' located?

I assume that your problem is that you want to view files before deleting them.

You might want to use free IrfanView.  It is much more powerful and versatile than Windows Picture and Fax Viewer.

The reason you can't find WP&FV is because it is in a cryptically named dll file.  The following is courtesy of MS-MVP Volunteer J (and assumes that you are using Windows XP):

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Try the following:

Go to...Start / Run...and type
         (or copy/paste):

regsvr32 /i shimgvw.dll

(yes, the space after the 2 and the space
after the i is required)

Press...Enter...

You should see a dialog box that says:
DllRegisterServer and DllInstall in shimgvw.dll succeeded

Now...the following command should launch a blank Windows
Picture And Fax Viewer screen. It will say: No Preview Available.

rundll32.exe c:\windows\system32\shimgvw.dll,ImageView_Fullscreen

Now set WP&FV as your default viewer and you should be ready to view photos.

Open a folder and right click right click a photo...

From the menu...choose...Properties / Change Button...

Select Windows Picture And Fax Viewer and click...OK / Apply / OK.

Let us know the exact result.
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Windows Picture and Fax Viewer is just that...a viewer...
no photos are archived in Windows Picture and Fax Viewer

I would suspect the unwanted pictures are in your
Temporary Internet Files folder. When you access
sites on the net that include graphics and pictures,
they are loaded into this folder so you can view them.

If you would like to view the contents of your
Temporary Internet Files folder...try these steps...

Go to...Start / Control Panel / Internet Options /
General tab / Browsing History section / Settings
button / View Files button.

Or...open an IE window and go to...Tools / Internet
Options / General tab / Browsing History section /
Settings button / View Files button...

Also you could go to...Start / Run...and type or Copy/
Paste  the following command:

%USERPROFILE%\Local Settings\Temporary Internet Files

Then press...Enter...to launch the Temporary Internet Files folder.

To clear it up...try deleting your Temporary Internet Files.

Running Disk Cleanup should take care of it.

(310312) Description of the Disk Cleanup
Tool in Windows XP
http://support.microsoft.com/?kbid=310312

Also, on an Internet Explorer window...you could
go to...Tools / Internet Options / Delete Files / OK.

Do it again and check, "Delete All Offline Content" / OK.

Delete Cookies Button / OK.

More info...

Safely Delete The Temporary Internet Files
http://mvps.org/winhelp2002/delcache.htm