Doug,
I had the same problem...I just ripped up the rug and used a primer. I used clear polyurethanne to cover any stains and kept on painting. It took a couple of coats but it was an inexpensive alternative to putting down anything else. Anyway...if you dont like it..its just particle board right. mine looks good though, I did a faux finish and it looks like marble, then I coverec it with a few coats of urethane and it costs under $100.