My father has an old HP 8100 which he still uses. For a while it was producing some of the same symptoms you described. He has Win XP.
No matter what he would do it only burnt coasters. Rather, you could start a new session, but it didn't matter how long you left it burn, it never really wrote anything. You can't make a music CD with one of those disks, but I found I could start a new session...that is, after I fixed the problem.
The only thing is, it was a while ago and I can't remember what I did! It was definately a software problem, because I didn't mess around with the burners' firmware or anything. I think what I would do first is check to see if someone else can make a multisession disk out of those coasters you have. If your burner isn't destroying the CD's with junk data, then you might have hope. If someone elses CDRW says that the disks have stuff written to them, but it can't read any useable data, then it probably is time to get a nice new CDRW.
I HIGHLY recommend LiteOn drives.
Very very cheap, very very fast, copies practically everything. Pretty much the best in the buisness. At least, 95% of the best at 40% of the cost!!
It's been a long time now, but I think the 7100 was the Philips-based model that suffered from the "gummed up" laser transport rails. Opening the drive, cleaning the rails and applying a light lubricant sometimes restored them to use.
Of course, that was back when drives were quite expensive. A drive that runs ten times faster than that old clunker can be had for very little these days.