|"an old 286 comp"|
"Premier 1100, (1986) PC."
Not enough info.
Is Premier the brand, or the model series of another brand ?
286 computers often came with a MFM or RLL hard drive and a hard drive controller card to match, but they also often had a bios that would accept you using an IDE drive controller card in an ISA slot and using one of certain sizes of IDE hard drives ,selectable in the bios, rather than a MFM or RLL hard drive .
Usually you had to use a specific floppy disk to access the bios Setup on early 286s - do you have that for your computer ?
If you don't, there are generic floppies available on the web that will probably allow you to see your bios Setup.
Your extended memory has nothing to do with the hard drive. That's either installed in the mboard, or installed on an extended or expanded memory card in a slot plugged into the mboard.
Early 286 computers had sockets for individual memory chips, rather than ram modules that had more than one memory chip on the module that plugged into a ram slot. If your mboard has the individual chips in sockets on the mboard, or if you have an extended memory card that is installed in a card slot that has that, they were notorious for developing parity memory errors because of "chip creep" - the chips moving in the sockets because of the warming /cooling cycles the computer was exposed to, causing a poor connection of one or more chip to it's chip socket..
If you remove the power to your computer and carefully pry each chip upwards a bit and push it back down, your parity memory errors will probably go away.The chips for extended memory would be in a specific area - for above 640kbytes.
Or you could try just pressing all the chips down in their chip sockets.
Some mboards had only enough chip sockets to install max 640kbtyes on the mboard - some had enough to install 1mb (1,024kbytes ) on the mboard.
286 mboards made slightly later had individual chip sockets and SIPP or SIMM slots for ram modules.
If you wanted more ram than that, you usually had to have an extended memory card installed in a card slot and have memory chips installed on that.
How much ram do you have installed, total ?