With Windows XP, after each power faillure, windows would run chkdsk to check the hard drive. However, i do not see this pattern with Windows 7, even after a power faillure. Does that mean it does not need one or do i need to run it manually?
NTFS has become much more of a "journalling" filesystem seemingly during the lifetime of Windows XP and has adopted a lot of features that make chkdsk unnecessary. Together these technologies mean that running chkdsk is largely unnecessary as the state of the filesystem is much easier and faster (e.g can be done quickly during boot) to determine and restore to a "known-good" state.
Windows Vista introduced Transactional NTFS which appears to be similar in principle to a journalled filesystem where specific check-disk type events should be rare or unnecessary. Essentially when the filesystem is mounted it is easy for the driver to find out what happened before the power failure and very quickly determine whether to roll-back, roll-forward or simply discard changes.
(I believe the major changes appeared in Vista as I have not seen chkdsk run at boot since moving from XP)
As mentioned in the comments there are cases where these systems do not protect you and it is entirely possible for your system to become corrupt to the point where chkdsk is necessary, especially when using file systems that do not support these advanced features such as the FAT filesystem used on Flash memory sticks. These features are there to reduce how often chkdsk is required during boot by making it easier to determine the filesystem state prior to unexpected power down.
As a side note I have even started resizing a disk using the disk management console, realised that I had to power down the machine mid-resize as it was taking a long while. I assumed it was at a point where I data loss was guaranteed, but when I rebooted I found everything was perfectly in-tact, back the way it was before and nothing was corrupt or missing. I don't recommend trying this at home as you could loose everything, but "yay" for Microsoft protecting me against my own stupidity.