What files are you trying to delete? Deleting through the Search isn't very effective, and you want to delete hundreds of thousands of files...
Also, I do not think the search brings up those files because they're hidden? Try enabling hidden files/folders.
Open My Computer.
Select Tools > Folder Options from the dropdown tab on top.
Select the View tab on top.
Look for the category Hidden files and folders.
Choose the option 'Show hidden files and folders'.
I hope that helps.
Note: If you're looking for a virus in your computer, please read here
for more instruction on how to clean up your computer.