I Think My Home Network May Be Receiving Attacks?

These are what I use:

Router: D-Link EBR-2310, latest firmware, 2.01

Two computers off of this network, one running winxp32 SP3, and one temporarily running win vista 64 sp1 (soon to be moving to winxp32 sp3 again...)

I run Bitdefender total security 2009, all settings on max and firewall on "ask".

I also use adaware, free version for a few scans.

Story:

I had a "friend" in another state who started acting funny about things, he then "slipped up" in a phone conversation and said something that no one else would know unless they were watching my IRC private messages. (I was doing a pre-interview with a programmer in California.), this "friend" accidentally brought it up, though I NEVER told him ANYTHING about it. There were a few other funny things around that time. He was probably watching me, he also brought up getting into hacking.

This person has moved, has given up his cell phone and has completely dropped off the radar. Even if I call the cops on him, or maybe even the feds, I doubt they could find him easily. He turned from an okay guy to, as you can tell, a questionable person which was why I started ending our friendship, though nicely. (He lives in Vegas, I live on the East Coast).

These are my symptoms:

I do a virus scan probably once a week on both machines, along with adaware, I seem to be free of everything, but as I have learned in the past, custom scripts can be written to bypass all of these security programs. I once logged into my router to see an active session from a Walmart, which seemed odd, but maybe that was nothing... I will be watching these again tonight due to the below odd happenings.

Vista64 machine:

Sometimes my bitdefender is shut off when I come back to my freshly installed OS.

Sometimes random programs are opened, like today I come to sit down at my pc and a random .gif was opened twice in a program which I would have to "open with..." to use. I can not see anyway this could accidentally of happened.

Vista 64 seems to randomly crash with zero reason... this could just be vista 64 though....

As I write this, I go to click on bit defender and it seems to have crashed or stalled, yet I've never seen this happen, after years of use and am only browsing the net.

XP32 machine:

Hard drive light goes off randomly. I recently had to replace my last hd on this machine due to a head going bad. I then learned that viri can be written to just read/write one area thus wearing out the HD. Tonight, on a newly installed OS, fresh format, all protection on max at etc. No programs were on, yet the HD light was blinking away, about a blink a sec, the computer had no reason to do this. No updates, no programs running etc etc, VERY odd.

I went to save a document on this same machine earlier today, and as soon as I almost click on "save as", the program, Word, freezes completely. Now, this is a simply word doc, a few paragraphs of text and I don't believe I've had word crash on me for years. Odd.

Please remember both of these OS's are pretty newly installed and once they are installed the first programs to go on them are win updates and your defender program.

Do I need a tin foil hat, or is this person in Vegas, or another person, screwing around with my network? I should also note that I run a small business from one of the machines.

Even if there IS some person screwing around, what could I possibly do? The police here are a laugh, they wouldn't lift a finger for something like this, yet my machines , like my last HD, seem to be under attack. Note, that hd was pretty new and the head just died on it? And now this new HD and new os install, the hd light is blinking for no reason.

There just seems to be too many things going on here.

I would love any suggestions you may have. I suppose all I can do now is watch for any odd router sessions and mark them down, whatever good that does...

Thank you for your help.