
Though I'm not a native, I'm pretty sure it should be
你是什么时候开始用电脑的
(什么时候 instead of 什么的时)

+1 to sysko's comment
And also since this is a question, the 。 should be replaced by a ?
Though I'm not a native, I'm pretty sure it should be
你是什么时候开始用电脑的
(什么时候 instead of 什么的时)
+1 to sysko's comment
And also since this is a question, the 。 should be replaced by a ?