My rig system as write at the signature

Graphic Card
Gecube X300SE HyperMemory 256MB

Standard Clock
Core = 325MHz
Memory = 200x2 = 400MHz

I used AtiTool 0.25 Beta 10 to find my max core n max mem and here's the result without an errors

Overclock
Core = 499.50MHz
Mem = 516.38x2 = 1032.76MHz

Addtional info
At the gc, there's only an original heatsink(without fan) cover the core chip n no other heatsink placed on my memory..!!

now i placed my rig in the air-conditioned room..!!
0.6A fan blow the air to the gc
I want to ask that

will this overclock settings can cause my gc get harm??
or other effect i will get??