Only DOS (with drivers) and programs that can boot from CD/DVD can run from UBCD as its not an Operating system but a CD of tools.
Well, actually, programs that can boot from floppies and programs working in real DOS mode, not only CD/DVD, can be run from UBCD.
Best bet is to press f8 before windows 7 starts, boot into safe mode and run those scanners. If they will not run, download on another computer Spybot S&D and run it, as it is meant to run from safemode and WINPE environments and have personally run it myself and saved many computers before. Spybot will only detect Malware but not viruses, same with Malwarebyes Anti-Spyware; Be warned.
There are many live CD's from antivirus manufacturers, if the anti-spyware ones above mentioned are not enough.
Just be aware of updating the anti-virus definitions / databases before actually burning the CD. The same goes to the antivirus tools included in UBCD.