If you're no where near full, I wouldn't get anything larger as you may run into BIOS issues. Do you know if the drive is SATA or PATA? I know that drives of that size are still available but may not be for long. 160 GB easily holds any Windows OS and tons of software. Any greater need might be better filled by supplementing it with another drive such as an external.
I have an older desktop with an 160GB hard drive that I want to replace. Do I replace it with the same 160 GB or should I go for larger. If larger, what size is recommended? Thx

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic