English PC

I moved to London last year for my job.
I brought a PC which was installed windows for Japanese.
Unfortunately, it crashed and I had to buy new one.
Although it is not impossible to buy Japanese one in the UK, it was not affordable for me.
I bought new cheap one which was installed windows for English.
Of course, we can use Japaneses on it; read and write. However some software makes character corruption.
The iTunes did not deal with Japanese song name correctly. The video studio did not load video files correctly.
After coming to the UK, I did not use Japanese file name. Then it was ok. However, my old files sometimes use Japanese as a file name or directory name.
I was confused. Then I looked for solutions on the web and I found it; it said that I have to change "system allocation" setting from English to Japanese.
I tried and all problems were straightened out. I did not look them.