Windows 7 Won't Boot Any Live Cd..Not Even MS!!

Hi. For about 5 years, I made and used many different live cds. About a year ago I tried to make one and it wouldn't boot from the cd. The boot order has been checked and reset and checked and reset. It's not that.
What could be causing this? Everything else about the pc is great. No other issues. No malware. I cleaned the cd tray twice. No issue burning, just using. Not even MS cds work. Please advise as to what could be going on.
BTW, I have run sfc scannow and a thorough chkdsk. Thanks in advance for any help offered.

Thank you AddRAM for replying so quickly. The first thing I tried was to boot from a usb. Didn't work. Maybe I didn't burn it right, maybe I did. I don't have another pc to test out all the cds I have but there is no way that all of a sudden, more than 15 cds all of a sudden just went bad. Even the MS cd I got from my friend wouldn't boot...and he uses it all the time.
I tried looking in device manager for any yellow or red alerts, but there were no alerts for Cd-ROM. It was normal.

Query: Since the MBR is the 1st thing the pc goes to when booted, could there be an MBR issue. I checked it with aswmbr last night and it was clean but for "sptd.sys **Locked* 32. Don't think it has anything to do with my issue though. The cd tray burns normally. I have seen others online with this problem and in each case, the solution was always different. One guy, after trying 10 diff things unplugged his HDMI and then used a vga instead and the thing started working!! Go figure. I honestly don't think the cd/dvd is broken.

Once a Live cd is in and I turn the box on, the white cursor is blinking for a few seconds, then it just begins a normal boot. Then the Live Cd starts its cycle but doesn't boot. Is there any other solution you may have that could help me? It would be very much appreciated. Thanks.

Hello again. Thank you both for responding. I will try to make a bootable usb drive again using universal pendrive. Before I do I must tell you that I just listened to a cd on my box and watched a DVD. That's why I'm confused. I guess maybe the way boot cds work is somehow different. Anyway, as for WHS suggestion, I thot about Flashing. I'm SCARED to flash the BIOS! Bad stories I've heard about people basically roasting their machine.

Either way, I will try all of these suggestions. I just don't get how I can use my CD/DVD tray for all other uses with no issue.
Is there a way, a test I can perform that will tell me the health of the optical drive? The health of the BIOS? Any software suggestions? Thank you.

Hey guys. I will look to see if my 2007 acer has a boot menu key. If it does, I will immediately try your suggestion. And yes, this machine can boot from usb. I put it in that mode before but it didn't boot. Maybe because I didn't do what you both just suggested. We'll see shortly. If all else fails, I will follow your usb instructions.

I don't press anything after turning on the pc. With the boot cd in there I just wait for the screen to come up like it used to. Maybe I havent done this in so long I just forgot how. Your instructions are clearly spot on.

I must tell you this. I have tried booting more than 10 times without success. It just goes to the desktop.
3 days ago I ran sfc scannow and checkdisk. Then attempted to boot. For the 1st time ever..it Bluescreened!
That made me think it was somehow software based. I took out the cd and rebooted to the desktop without issue. Hmmm. Windows showed Files that help describe the problem". C/windows/minidump/050715-33977-01.dmp and c;\users\user\appdata\local\temp\WER-158575-0.sysdata.xml.
I will now request Windows look up the error and then perform the boot menu key approach. Thanks a lot guys.
Your help is truly appreciated.

WAHOOOO! AddRAM and TVeblem..you guys have your Stuff together. I used the 1 time boot key (F12) and saw Optiarc DVD RW. I tried this 2 weeks ago but thought that was the wrong one so I didn't select it. I did this time and for the first time in over a year I got to the bootable environment! COOL! I came back here because a few days ago I was on another help site and the guy didn't know jack. His "help" was embarrassingly useless. Thank you for getting right to a solution. All the best to AddRAM and TVeblem. You guys ROCK!! You are truly Windows Masters.