when i start up the com i get a message saying incompatable ms-dos version
i have used a 7.10a dos boot disk but it still displays the same message
how can i find the version of dos so i can use the appropriate version of dos?

You need to provide more details.

What are you trying to do? Why are you using a bootdisk? What exactly are you doing to get that message?

Typically that error is seen when trying to run Win31 using the DOS from Win9x.

The system files on your booting drive are not the same dos version as some command you're trying to run. If this is happening with the floppy bootdisk you need to get a new bootdisk--www.bootdisk.com

On the hard drive, if you must use a command from an older version of dos you need to make sure there's a line in config.sys that says:

device=c:\windows\setver.exe

The setver.exe file contains command names and corresponding dos versions and will force your OS to use them. The file can be edited to add entries. Type setver/? at the dos prompt for details.

Oh, and typing ver at a dos prompt will tell you the dos version of your system files.

Mixing versions usually generates the "incorrect DOS version" error - IF the message is being correctly reported (which is anyone's guess).