random system crashes

I run 10.4.11 of an intel G4. in he last couple of days it has started regularly showing the dreaded black reboot box. it seems to just happen if the computer is left unused for a while (with or with out sleep or screen savers enabled).
At the same time another fault started in that every time I try to open the applications folder it relaunches the finder, and so I cannot get into the applications folder. I have tried running disk utilities(opened by searching on searchlight rather than accessing through the application folder) but the reboot box appeared before it finished verifying
I cannot find the install disks, but have run software update and things like MacJanitor


Any ideas gratefully received

An Intel G4? The G4 is PowerPC.

What you're experiencing are "kernel panics" which usually means that hardware is failing or causing the problem. It can also be caused by software.

But without your original install media you have no way of doing a check of your hardware and hard drive. Disk Utility running while the system is active can not do any repairs if needed. And if hardware (hard drive) is at fault, DU may crash before it's finished checking.

Bottom line - is you need to obtain a copy of Tiger for your machine. If you can't purchase an original set, you'll have to go with a retail DVD. The only retail DVD of Tiger sold AFAIK is for the PPC. (Your machine.)

Regards.