Hi Ken,

The WBK file extension is primarily associated with Microsoft Word document (DOC) backup files. If the option is selected in Word, the program creates a backup copy, with the WBK extension, of any Word document so that the document can be recovered in the event of a program or system crash or if the file is corrupted, infected or accidentally deleted.

Deleting your web cache is a good way to speed up a slow internet connection. These files take up valuable resources that could be used to for a better net surfing experience. Remember that while you are online many files in the web cache are active.
Cookies are loaded in your browsers and constantly update themselves. Also your computer will search through the temp files to match the latest version of a web page.

So, by clearing the web cache you cut down on the work your PC needs to do thus speeding up your slow internet connection. Remember to shutdown the browser when deleting the cache. Because what files are open will not be deleted. Here how to delete your temporary internet files.

Manual steps to erase your temporary internet files.

• Quit Internet Explorer, Firefox, or any other web browser
• Click Start, click Control Panel, and then double-click Internet Options.
• On the General tab, click Delete Files under Temporary Internet Files.
• In the Delete Files dialog box, click to select the Delete all offline content check box , and then click OK.
• Click OK.

I hope this helps.

Regards,
Lokesh