Sorry.. I can only guess blindly what it could be..
I have seen many cases where the Java VM crashes or where the system hangs for a few seconds or also where Phex stops reacting.
Sometimes that can be solved by a Java update or a Phex fix.
But system crashes I have seen only very rarely. I know of a few BSOD cases resulting from incompatibility between certain network drivers and Java on high system load. But a different Java version or driver update tend to solve these problems.

The age of your computer should not matter much, you could configure Phex to run with low resources in 'leaf' mode. The only thing that might be a little low is memory. Java likes to eat memory! But I guess Phex should stay below 70-80MB if you don't challenge it to much.

Sometime there can be problems when there are multiple Java version installed on the same system, so you can try to uninstall all Java versions through "Add/Remove Programs" and do a clean install. Java is not very invasive on your system, so there shouldn't be any trouble with uninstall artifacts.

Gregor

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