Invalid e:drive

Go to start menu, at the run prompt, type in "diskmgmt.msc". This will bring up the disk management windows.

Look at the left hand column, What does it say for Drive E:?

If drive E: is shown as a CD-ROM then you will get the invalid message, if you try to save something to it.

What are the steps you took to try to download Windows Defender?

There is no e: drive showing at all. In the top white box, under Volume is (C. I the grey box underneath, on the left it says Disk and in the box next to it which has grey lines running diagonally, is (C again. Underneath Disk is CD-ROM 0. And that's all I see.
I am trying to download straight from microsoft downloads and when I try to run it just says e: drive invalid

Don't Run, use the Save option.

If other options don't work, then you're left to do things the hard way. Chances are your registry is messed up, and there are references to drives which once existed but no longer do. This can also happen if software was installed from a network at sometime in the past. If you're not already familiar with the Windows Registry and the program REGEDIT isn't familiar, then Stop Now, go no further! You can really mess up your system doing what I'm about to tell you, so it's not for novices.

Okay, so either you know what you're doing or you love taking big chances. Either way, here goes. Go into your registry (you're already familiar with regedit and how to do this, remember?) Search for data with the value of the "missing" drive. For example, you can search for E:\ to find drive e:. Change it to the drive you're really using, probably c:. Repeat this process until you've searched and replaced every occurrence. Again, if this isn't clear, then don't try it. I've intentionally not given detailed instructions because if you need them then you probably shouldn't attempt this. Even experienced individuals can really mess up their systems by editing the registry, especially when searching and replacing little bits of data throughout like this. It worked for me, but I know what I'm doing, and I have a death wish.

Good Luck!