It is very much personal preference, e.g. the functions you are likely to need/require and how frequently you are likely to us it.
If it is infrequently there are several free versions, just try a search for screen capture software.
On my win7 netbook I have Ashampoo Snap 5.5.1, which I got as a freebie some time ago, often it si easy to find them giving away an older version. Hoping that you may upgrade.
For those that use them more frequently, you may go for a paid version with more features. On my XP Pro desktop I use SnagIt 10.0.2 by TechSmith, a paid version.