The anime could be crappy I have 4Gb of ram
a Radeon HD 3870
graphics card, and am still forced endure problems like that on certain videos. Or it could be due to slow reading from disk - try defragmenting your hard drive. You can also try changing your player.
PS: graphics & audio cards have wery little to do with this, gaphics is only used in games, and sound will work enywhere the only diffrenece is quality.