Burning CDs

I have a number (quite a few) Cds which are approx 6 years old. They are TDK
CD-R74 Reflex. I used them quite happily with my previous PC, which I think
ran XP. I purchased a new PC eigtheen months ago but it will not write to
these CDs. It appears to go thru the motions using the "Wizard" but when
finished the CD is blank. Any ideas of what is happening please? By the way
I purchase some new discs and they burn fine.
—
Jonca of Sidcup