It's a good idea to always set a restore point before installing anything on Windows
Seriously - anytime you install or update set a restore point.
In this case though you can just uninstall ASIO4ALL and everything will revert. Windows Key -> Settings -> Apps -> ASIO4ALL
Mr Tuesday's youtube post on ASIO4ALL is a good example.
When you install ASIO4ALL it is now the driver you pick in REAPER - not the M-Audio. ASIO4ALL will inturn show you the M-Audio as one of the inputs and outputs.
ASIO by default is single connect. You can only have one application working with ASIO. If reaper is using the ASIO then other apps can't.
If you had setup the M-Audio to be multiclient where it could play Windows audio like from Youtube at the sametime you were using a DAW (Reaper) then you were not using ASIO. Windows audio is very latency prone no matter what the settings are. Multiple apps are all trying to use it at the same time.
Having said that, there are multiclient ASIO applications that work with ASIO4ALL. This isn't your goal now if you just want low latency with Reaper. Multi-client doesn't help with latency.
DPI-Latency checker is a good app to run to see if your PC is up to running at low latency.
Something is FUBAR with this system. I could select the ASIO4all driver, but couldn't select the M-Track. And no, I wasn't running multiple audio applications concurrently. And unfortunatly Win7 wouldn't let me restore to an earlier point. I had trouble getting it booted back after the failed restore attempt. Eeeeesh.