Advice on Migrating from Computer with Issues

I've just picked up a new computer and I'm looking for some advice on the best way to migrate from my old computer, which is suffering from numerous issues:

• Mail is an absolute mess. I have to input my passwords several times a week (sometimes for all my accounts, sometimes for some of them).
• Frequent hard freezes and sudden resets. There seems to be no rhyme or reason to when these happen, no common causes, etc.
• iCould syncing is extremely iffy. iWork documents can take days to show up, Clear (the RealMac App) syncing frequently shuts off.
• iMovie refuses to work with external libraries and won't export projects
• iMessage syncing is intermittent.
• Fan runs at full blast far more frequently than it should, and doesn't appear to be connected to machine usage (ie. Activity Monitor doesn't show anything that's hogging processor or memory).
• Numerous other small issues.

I've heard things like "if it's a software issue, migrating will just put that issue right on the new computer," and obviously I don't want this to happen. I'm typically fairly handy at trouble shooting, but nothing I've done as fixed any of these issues for any left of time. I've gone through the usual PRAM reset, trashing preferences, and gobs of problem solving walkthroughs and nothing has stuck.

 

I guess I'm just worried that if the issues are software related that all those issues will be transferred to the new machine. So, I understand that things like iCloud data, etc won't be "physically" transferred, but there are certainly some software bits and bobs on the current computer that may have issues that could be transferred over.

For example, I have dealt with Messages on my computer blanking all of my conversations numerous times, and then and that is a 100% software-based fix. (changing read/write permissions on the chat log files)

I don't have any personal experience with this happening, I've just heard numerous phrases like, "well, if the problem is software related and you restore your iPhone, it'll just put those problems right back on," or "seems like you have a slew of corrupt preference files, so those issues will get copied over to the new machine."

 

I'm unclear about what you mean by "simply signing into your account via another computer." The vast majority of what I'm talking about is related to apps on this specific computer (that could be hardware or software related) not web services that I can log into from any machine. When I mention "Mail," I'm talking about the Mail app, which I use with several Gmail accounts, a few Exchange accounts, and a Zoho account. None of these accounts are more problematic than any other.

The iCloud/iMessage problems I mention are unique to this machine. I am using iCloud/iMessage with two computers and two iPhones, and the computer in question is the only one I'm having problems with.

Exactly. If the source of the problems is hardware (which it may be), then the problems should be solved, but if the problems are software related then I'll still have to deal with them, and this is *precisely* what I'm trying to get advice on avoiding.