Starting the computer in safe mode may help. Repeatedly press F8 on startup.
If the disk is ABSOLUTELY full, I can see how there might be a problem in moving things to the recycle bin. You can force instant delete by holding down shift then pressing delete. Do a few files at a time.
Right clicking on the disk in My Computer allows Disk Cleanup to run. Once you have a bit of space, this may help. Then download the wonderful "Crap Cleaner" will help.