To control the appearance of the Windows Start Up menu, you can edit the MSDOS.SYS file. It's usually in the root directory of your boot disk. (C:\MSDOS.SYS on most systems.)
In this file, look for an [Options] section. Under [Options], be sure you have...
BootMenu=0
This will tell your system to NOT display the boot menu.
If you don't have a MSDOS.SYS file, you can create one. As well, if you have the file and it's missing the [Options] section, you can create it too. Just be sure you edit with plain ASCII text. (Use Notepad, not Word.)
Cheers, PW.
P.S. For those who wish to see the boot menu, edit the MSDOS.SYS file so that in the [Options] section you have ...
BootMenu=1
BootMenuDelay=5
This will display the menu for 5 seconds. After that, the system will boot using the default. You can indicate any delay. I use 5. Before I switched to decaf, I used 4. When I was younger and quicker, I used 3.