Laptop randomly freezing

[Bloodfire]

Ok, so I have this laptop, it's a toshiba duo core cpu, recent memory upgrade from 1 GB to 4 GB, win 7 pro 32-bit, and I can't seem to figure out why it is freezing at a certain point.

It always seems to lock up when left on for extended periods of time, usually 12-18 hours, and the lock up trigger is when you open a web browser. At first I thought it was memory shortage since I was running win 7 on 1 GB and a 4 GB flash drive w/ readyboost, but it had been freezing even before I upgraded the memory. Since the upgrading the memory did not quell the freeze issue, I can only think it might be an overheating issue. Question is why is the web browser the thing that causes the lock up to occur?

Any input would be helpful, thx much in advance.

[Kongolo]

1- whats the model number?
2- which browser?
3- when it started?

[xerodok]

Does web browsing work flawlessly otherwise?

[Bloodfire]

@Kongolo
1- Toshiba Satellite A215-S5824
2- IE and Firefox
3- sometime after I used readyboost on the system, Though I speculate installing win7 on this system may have a hand in it. On the other hand it came with Vista pre-installed, and that OS is not drastically different from win7 to think there could be an issue.

@xerodok
If it does not lock up, the computer works fine, browsing included.