BSODS at startup

Vista Ultimate 64 bit
All of a sudden I am experiencing serious problems at startup.
Bluescreens, random services stopping, etc.
Although when I do manage to get system on and stable, it is as solid as a
rock with no problems.
Trouble is a restart then starts it all over again.
At the moment it is a nuisance, but I am concerned what will happen when I
have to reboot after installing or updating something in the future.
I have tied uninstalling anything I think could have contributed to this but
its still there.
System restore has various entries, but doesn't go back far enough for me to
restore everything exactly as it was when the system was definitely OK.

Is there any way to open up earlier system restore points so that I can go
back far enough to eradicate every last residual scrap of whatever is
causing the problem ?

Anybody else had something similar and managed to solve it ?

Any suggestions welcome.

Phypps