Holy smokes I got it to work!!
Here's what I did:
-With Xperia x10 UNPLUGGED,
-Went into Device Manager
-Clicked on VIEW, clicked on SHOW HIDDEN DEVICES
-Highlighted SEMC Mass Storage Device, clicked DELETE
-Hooked up Xperia x10 to USB cable
-FINALLY GOT THE OPTION TO CHOOSE MY DRIVERS AT THIS POINT!! (YAY!)
-Directed Device Manager to x10a drivers I downloaded
here.
-Computer installed Sony Ericsson sa0101, underneath it said Sony Ericsson sa0101 ADB Interface Driver
-Computer also installed SEMC Mass Storage Device AGAIN, but I clicked on and DISABLED IT
-Went into SWM, ran and passed all diagnostics
-Tried to install Backup and Restore apk by Sony Ericsson, got a No Free Space error
-Long story short, I opened a DOS prompt, navigated to c:\AC_SWM
-Changed the name of Backup and Restore.apk to bakup.apk and copied it INTO AC_SWM folder, NOT PAYLOAD folder
-Typed in this command:
adb install bakup.apk
-SUCCESS!!
-Went to Applications on my phone, and its there!!
HOPE THAT HELPS!!
(SORRY GB, EDITED OUT MY ORIGINAL TEXT)