I played and beat ME1 on a 360, but no longer have that 360. Now I have a PC powerful enough to play ME2. Should I get ME1 and replay that just so I could have a save file, or should I just play ME2 fresh?

Since you already experienced Mass Effect 1, if you want to jump right into ME2 there's a save repository that can recreate some of your decisions from the first game.  Of course, if you want to go through the first game again, its certainly a worthy endeavor.
 
Part of the fun is carrying your Shepard through all three games, but I wouldn't delay ME2 further if you don't want to replay the first one.

There are a couple of sites with save files and descriptions of what choices were made in the game.  Download the one that closely resembles your ME playthrough and play ME2.
 
[edit] Here you go:  http://www.masseffectsaves.com/

I'd play ME1, heck did it 4 times than 2 times when ME2 came out.

A new $20 copy of ME1 along with the DLC that comes with the box and none of the glaring choices that were made for the fresh ME2 Shepard? I'd say that beats C-Sec...I mean a fresh ME2 run-through.
 
Edit: Forgot the PC part. I'd say go with Andorki's reply.

I agree with Andorski. Head over to masseffectsaves and download/import the save(s) that match the choices you made as closely as possible. 
Of course, Mass Effect 1 is a superb game, so if you want your save import to be perfect, replay Mass Effect. It's worth it.

You might wanna replay it, just go get back into the vibe and be on first row for all your choices and stuff, better then editing files or what not in my opinion.
I loved ME2 because it really referenced ME1 in a lot of ways and it made the game so much better for me.

Play Mass Effect 1 on your new PC! The first one is so much better anyways.

I hated playing ME1 when I first did it. Then, I finished ME2, realised how much I'd missed out, and played ME1 again. And then again, and one last time for the l60 transfer. Now, I'm doing ME2 again...

Play ME1, its still a great game and i'm sure you'll be glad you did when you have all that history when ME3 hits.

Deffos do ME1 again. It's the only way. That way you can be exact and having all that fun stuff.

I'd replay ME1, just a personal preference.

I played them backwards (ME2, then ME1), and thoroughly enjoyed both experiences. The importing of the save file seems kind of gimmicky, honestly.  The two games are both really great, in their own ways. By playing ME1 after ME2, I was really able to appreciate some of the design choices that were made in the second one.  They are really almost like two separate games.  ME2 plays like a great modern shooter, and ME1 veers pretty far towards the realm of KOTOR. At first I was really annoyed by all of the inventory management in ME1, but it grew on me and in the end made the experience richer.