A corrupt RAM (Random-Access Memory) might bring on the blue screen of death(BSOD) with a message saying Fatal Exception Error. A fatal error indicates a serious hardware problem. Sometimes it may mean a part is damaged and will need replacing.
But a fatal error caused by Ram might be caused by a mismatch of chips. For example, mixing a 533Mhz RAM with a 667MHz, will usually force the computer to run all the Ram at the slower speed. This will often crash the machine if the Ram is overworked.
For this it is advisable to use RAM with similar speed and capacity. Most of the time resetting the RAM by removing it out of the slot will fix the issue.
Parity error messages also refer to Ram. Modern Ram chips are either parity (ECC) or non parity (non-ECC). It is best not to mix the two types, as this can be a cause of trouble.