DVD burning problem

Can anyone help here? There’s a wealth of information on the internet, but it’s all rather confusing as to what the problem/solution might be.
With an Acer computer I’ve temporarily inherited and the help of a friend who introduced me to torrents, downloading music and movies as well as giving me a bona-fide Nero 9 package, I’ve been happily burning away. Now my dvd drive has a problem.
It will still read audio cds, vcds and dvds, burn audio cds, but will not now burn dvds.
In inserting a blank dvd disk into the drive, I get a kind of clunking noise, suggesting the disk is not being ‘accepted’. However, it seems to finally settle and the burn process appears to happen, but on Nero a message pops up to the effect that ‘the disk is not empty, do I want to erase and continue?’.
My understanding is that there are two lasers at work in the drive? Could the dvd one have a problem – although the drive still reads dvds. Could it be a software (Nero) matter? As far as I know, I’ve done nothing on the computer from when the drive was working 100%.
I’m having to drive into Udon today, will take the drive to just enquire on the cost of a direct replacement (not that expensive?), but will kick myself if it’s something which can be sorted on my current drive.
Thanks.

Rather as you indicate Brian, the problem could be down to 1 of three issues.

1. The software..
There are plenty of free programs to burn dvds on the net. Download one of them & try & burn a dvd. If it does not work either then you can really rule out a software issue.
2. The Media...
It is possible that you have a bad batch of blank dvds. If they were stored near a magnetic source then that can quite easily happen. Borrow a blank from a friend & see if that works. If it does not then it is doubtful that it is a problem, unless you & your friend bought from the same shop..
3. The Hardware.
A drive can go on reading long after it stops writing, or vice versa I guess, although once they stop reading people give up on them quickly..
A new writer for a laptop (which I assume is what you have) I am unsure about, but I would imagine that they are more expensive than for a tower & a bit more complex to fit as well.
For a tower a replacement is in the 600 baht range.
A separate, stand alone drive, which plugs in through a USB port is about 1,200 to 1,400 baht, depending on the write speed..

Thank you for your help and structured reply, Bob.
On my travels today, a guy unexpectedly cleaned the drive, particularly the lens and a general ‘hoovering’. I returned home, hoping this might have fixed the problem, but no. But, as you indicate, the cost of a new drive is inexpensive- I was quoted 800 to 1200 baht, although the technicians had different views on the best make.
I’m sure there’s no problem with the actual dvds. I must have recently downloaded 30 programmes successfully from the same box, before this hiccough. Not left in the sun, or near to anything which could mess them up.
I did try another burner, as you suggested, but it wouldn’t write. This gave me a message that no dvd disk was inserted – but it was. So it certainly suggests the problem is with the drive itself. Again, it made this whirring + slight clunking noise, like it was trying to load but couldn’t. Just strange when putting a CD in, it runs normally.
I do actually have a desktop/tower computer.
A new drive seems needed, hardly a fortune. But with your suggestions, at least I’m confident the problem isn’t elsewhere.
Fixing actually seems very straightforward.(Shame I won’t have a need to download Palace in the Carling Cup Final. )

If it is a tower then it is easy to fit yourself Brian.
A few screws hold the drive in place & there is a wide, long & flat 'data' cable & then three wires connected to a bulker connector for the power. It is as near impossible as makes no difference to incorrectly add the cables wrong when replacing..

As far as which make to buy I think they are all much of a muchness, to be honest.
The quicker the write speed the more expensive but, when actually recording I have always found that it is safer, or
probably the word is more reliable, not to record at the maximum speed.

I agree that a new drive would seem to be the issue. 1,200 seems a bit over the top for price. Personally I would aim for below the 900 baht mark for something that should write a DVD at over 20* speed - & get them to fit it for free at that price as well...
It should come with at least a 1 year guarantee, so it still will be good for recording the Palace push for the Premiership next year!!

Thanks for your input.
Even I've managed to take out and put back the drive on several occasions - and no parts leftover!