Unfortunately, even if you paid the general contractor in full, sometimes a subcontractor or supplier can still record a mechanics lien, if they do everything right and in a timely manner.
Did you get the preliminary notice before or after the windows were received and installed?
If the notice was more than 20 days after the receipt or installation or the windows, it is probably too late.
How long ago was the work completed?
Was a notice of completion recorded, and if so when?
It's possible it may be too late to record a lien.
This is NOT legal advice, just a general discussion of the law, as we are not familiar with the specific documents and facts of your case, etc. Please consult with a competent attorney in this area of the law for specific legal advice regarding your particular case, as the advice may vary depending on the facts.
I agree with Mr. Wolff. The supplier's Mechanic's Lien rights will depend on whether they followed all procedural technicalities and met all deadlines. It would probably be worth your time consulting with a construction attorney to go over these issues in detail.
No information you obtain from this answer is legal advice, nor is it intended to be. No attorney-client relationship is intended or formed between the questioner and answerer. You should consult an attorney for individualized advice regarding your specific situation.
I agree with the above responses, but would add the following. Assuming the lien is good, you may still be able to go after the general contractor (the dealer) for conversion, despite his bankruptcy. Depending on the amount you owe to the supplier, it may or may not be worth your time and money. If, after you speak with a construction attorney, it turns out that the lien is good, I would also speak with an experienced bankruptcy litigator to see if it is feasible to go after the dealer.