Muggles' Guide to Harry Potter/Characters/Borgin

Overview
Mr. Borgin, a stooping man with greasy hair and an oily manner, is one of the owners of Borgin and Burkes, the Dark magic supplies store in Knockturn Alley. The other owner is, or was, Caractacus Burke.

Chamber of Secrets
Harry enters Borgin and Burkes accidentally, on his first attempt to use Floo powder. Seeing Draco Malfoy approaching, he hides, and eavesdrops while Draco and his father Lucius are waited on by Mr. Borgin. In a particularly oily manner, Borgin suggests that it is a pity that blood purity counts for so little these days, expresses surprise that Mr. Malfoy is selling rather than buying today, commends Draco on his interest in the Hand of Glory, and finally bows the two of them obsequiously out of his shop. He then returns into the back rooms of the store, giving Harry the chance to make his way out unimpeded.

Half-Blood Prince
Harry, Ron, and Hermione follow Draco Malfoy, who has slipped away from his mother, to Borgin and Burkes. There, we overhear Draco demanding assistance in fixing something, a demand to which Borgin expresses some reluctance. Draco shows him something to inspire his cooperation. Draco also says that Fenrir will be stopping by periodically to ensure that he is doing his job. After he leaves the store, Hermione goes in to try and find out what Draco had been interested in; Borgin is uncommunicative, though he does mention that one necklace she looks at is priced at one and a half thousand Galleons. Finally he ushers her out of the shop, and puts up the Closed sign.

While we hear that Tom Riddle had been employed some years earlier at Borgin and Burkes, we do not see Mr. Borgin in relation to that employment.

Strengths
Borgin appears to be very knowledgable about the magical properties of the items that he sells.

Weaknesses
He seems to be pretty easily cowed into cooperating with Draco Malfoy once he realizes the latter's association with the Death Eaters.

Relationships with Other Characters
He is apparently well acquainted with Lucius Malfoy, as shown by his sycophantic behavior towards the influential pure-blood. Judging by his comments after Malfoy leaves the shop however it seems that Borgin resents if not outright dislikes him.

Greater Picture
It's unknown if he was the original Borgin who opened the shop with Caractacus Burke in 1863. If he really did start the business then he would be around 150 (or likely even older) during Harry Potter's time. Though it's clear through the text that Borgin is an old man it's unknown if he was meant to be that ancient. He did not however seem to work at the shop during the 1940s. It's possible that he is merely a descendant of the original Borgin.