A lot of things got affected. Most of it was harmless though, but it wasn't just the bottom-of-the-barrel software.

I'm just copy-pasting this source since I have it open from another comment in this thread.
These were the issues in Korea:

Four hospital patients in the southeastern city of Taegu were issued medical fee receipts dated Jan. 1, 1900. Plaintiffs and defendants in Suwon, south of Seoul, were ordered to appear for trial Jan. 4, 1900. A newborn baby's age was recorded as 100 years old at a hospital near Seoul after the computer malfunctioned in the transition to 2000.

The millennium bug also caused a heating system at an apartment complex near Seoul to malfunction, leaving residents without heat and hot water for hours. The ministry officials said the software error was quickly fixed.