Everything crashing on second-hand PPC g5 running Leopard!

Question

I just bought a 1.8 GHz g5 PowerPC running Leopard from my university's Surplus store. Supposedly they wiped the HD and installed Leopard, but I can't install a variety of applications because they keep "quitting" "unexpectedly."  My primary objective is to download a compatible version of Adobe Flash Player, but other forum answers have not provided the solution. HEEEELP MEEEE!!

Answer 1

1. Reinstall the software, then repair permissions as well as the hard drive:
Repairing permissions is important, and should always be carried out both before and after any software installation or update.
Go to Disk Utility (this is in your Utilities Folder in your Application folder) and click on the icon of your hard disk (not the one with all the numbers).
In First Aid, click on Repair Permissions.
This only takes a minute or two in Tiger, but much longer in Leopard.
Background information here:
http://support.apple.com/kb/HT1452?viewlocale=en_US
and here:
http://docs.info.apple.com/article.html?artnum=302672
An article on troubleshooting Permissions can be found here:
http://support.apple.com/kb/HT2963
By the way, you can ignore any messages about SUID or ACL file permissions, as explained here:
http://support.apple.com/kb/TS1448?viewlocale=en_US
If you were having any serious problems with your Mac you might as well complete the exercise by repairing your hard disk as well. You cannot do this from the same start-up disk. Reboot from your install disk (holding down the C key). This can take longer than a normal start-up.  Once it opens, select your language, and then go to Disk Utility from the Utilities menu. Select your hard disk as before and click Repair.
Once that is complete reboot again from your usual start-up disk.
More useful reading here:
Resolve startup issues and perform disk maintenance with Disk Utility and fsck
http://support.apple.com/kb/TS1417?viewlocale=en_US
For a full description of how to resolve Disk, Permission and Cache Corruption, you should read this FAQ from the X Lab:
http://www.thexlab.com/faqs/repairprocess.html
2.
You can check here:  http://www.adobe.com/products/flash/about/  to see which version you should install for your Mac and OS. Note that version 10,1,102,64 is the last version available to PPC Mac users*. The latest version, 10.2.152.25 or later, is for Intel Macs only, as Adobe no longer support the PPC platform. Note that the latest Flash Player update only works on YouTube with Safari in 32 bit mode - until YouTube correct this.
* Unhelpfully, if you want the last version for PPC Macs, you need to go here:  http://kb2.adobe.com/cps/142/tn_14266.html  and scroll down to 'Archived Versions/Older Archives'. The first one on the list, Flash Player 10.1 is the one you download. More information here:  http://kb2.adobe.com/cps/838/cpsid_83808.html
You should first uninstall any previous version of Flash Player, using the uninstaller from here (make sure you use the correct one!):
http://kb2.adobe.com/cps/865/cpsid_86551.html#prob1=uninst,os=m10.6,
and also that you follow the instructions closely, such as closing ALL applications first before installing. You must also carry out a permission repair after installing anything from Adobe.