URGENT! shared memory realm does not exist

I have an Oracle server running (Personal Edition 8.1.7) and on that I'm using two databases. When my machine starts up I try and access one of the databases and I get the following error:

ORA-0134: ORACLE not available
ORA-27101: shared memory realm does not exist

Some times this happens for both my databases, sometimes just for one of them, sometimes for both.

I have absolutely no idea why this is happening but from looking around in Google if I:

Run: svrmgrl.exe
Then I type: 'connect internal' followed by the password. Then: 'startup open'

This causes both databases to startup again just fine. However, this machine is going to a client as a demo and it will be restarted often! How do I solve the above problem without having to resort to svrmgl.exe every time? This is really urgent!

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Cheers,

elziko