Well, you've got a relatively modest computer, and it may well be having trouble working with those intensive 1080p files.
This may be compounded by the fact that you're editing in version 10, which does not support 1080p AVCHD video.
What are your project settings, as listed under your Edit menu? The closer your specs are to your video, the better the program will perform.
it says it on HD 1080i
so getting a newer editing software would help?
because i feel like its the computer, like when i take photos it takes forever for them to preview just on the computers previewer.
Yes, an upgrade to version 11 or 12 would likely resolve a lot of these performance issues. But what are the exact specs of the video you shot? (Your camera shoots 1080 in 24, 25 and 30 frames to per second.) It's possible you can come close to matching your video specs in your current version.
Your computer is still a bit underpowered for high-def video, however. So you can only improve performance with video from this camera so much.