If this is a new computer, you may simply have some bad memory. Try taking out a stick for a few days (if you have two) and if it still crashes, put the other stick back in and take out the first.
If this is a computer that worked fine with a previous OS, it still could be a bad component, but less likely. Have you downloaded and installed all the manufacturers drivers, or just used the built-in Windows ones?
Heat can be another issue, as well, as flaky power supplies.
When you installed 7, did you install it onto a newly created partition?
A common side effect of faulty memory is data corruption, so what I usually recommend in severe cases where there are a lot of memory errors, or memory is likely to have been faulty for some time is a clean install to clear any corruption.
Run MemTest:
http://www.memtest.org/
Let us know how you go.