I'm a small developer in VB6 and VB.net, and use for bugtracking a simple Excel. Seemed to me that I didnt need anything more.
I've wanted to add links to the code. Then:
How can I do it for vb6 and for vs.net?
Is this reasonable? Should I change to a (free) bugtracking tool? Do they have this functionality?
There's a list of bug-trackers in this question.
Do you want to link source code changes to particular bug fixes? That means integrating your bug-tracker with your version-control / revision-control system. (You do have version control, right? It's essential.) You could check the Wikipedia bug-tracker comparison table looking at the revision control integration column.
FogBugz is popular on StackOverflow, I hear it does integrate with version control, and it is free for one-person companies. Disclaimer: it was developed by a founder of Stack Overflow, so that may bias StackOverflow users in its favour slightly.