BleepingComputer.com: Another 16 Bit MS Dos Subsystem/NTVDM.CPU errors

I am running Windows XP in a 5 year old system. As you would expect its startup has gotten slower over time. I ran an advanced system optimizer v2 to try to improve performance. It did, but after that i noticed that i get two errors on start up. Two black dos screens open up. The first is labelled 16 Bit MS Dos Subsystem c:\documents and settings\all users\startmenu\programs\startyo\adobe Acrobat Speed Launcher.lnk. The second is similar with a file name powerr-1.exe. Then little error messages pop up related to these as follows: NTVDM.CPU has encountered an illegal instruction.... It then gives me the option to ignore or cancel. If I select ignore, the message pops up again. If i cancel then it disappears and my computer seems to work fine, for a few minutes and them it crawls to a halt. Restoring from the optimizer changes has not resolved the problem. Any suggestions are appreciated. Thanks.