Sorry for the delayed reply. Due to a problem with my USB keyboard (that's another story), I could not access the BIOS, until my PS/2 keyboard came the other day. I found what I was looking for - IDE UDMA - DISABLED. I have no idea how this happened, but anyway, now it's back to "AUTO" (there is no "ENABLED").
I thought the problem was fixed - my first few CDs were fine (using source files which has previously skipped every time) - but now, sadly, the problem has resurfaced with a new CD (I checked by burning the original "problematic" CD, and guess what, the skips are in the same place...). So something has "switched" the computer back to burning erroneous data. UDMA 2 is still the transfer more for my IDE channel, so (this time) it's not a Multi-Word problem. I have tried burning with each of my 2 RAM chips on their own, but this does not fix the problem - thus eliminating RAM (I think).
In response to your BIOS/motherboard suggestion - this is another problematic area - my PC is made by Advent, who produce computers for PC World and other UK retailers, and the motherboard is identified by Sandra as a Trigem Freeline series, which I can't find anything for. The BIOS is Phoenix AwardBIOS 6.00, which I thought was quite common, but I can't seem to download an update for that either.
So where do I go now??