According to BIOS FAQ link there is no data about that situation
FAQ page do not mention BIOS upgrade for model T2150CDT (PA1186) at all.
2. All ways of BIOS upgrading at Toshiba FAQ page says that upgrade utilites processes automatically.
But bios upgrade utilite for model of my Toshiba notebook do not processing automatically, it request to type "BIOS file name"
There is nothing about such request nitgher in documentation of notebook nor at linked page.
3. I do not know what bios upgrade utilite is correct cause of BIOS version at Toshiba archive support page
URL http://support.toshiba.ca/support/download/files_Archive/Index/bios_upgrade.htm URL
is B2150CDT.EXE of 04-24-96 v5.10 - Toshiba T2150CDT
but really my Toshiba T2150 has BIOS v2.0 not v.5.10 at all