Dont know whether this will help but here goes...
I have a couple of computers and some others which I intermittently use. My dekstop is reasonably old but its a HP and has XP (a good combination). So its pretty solid, now I was pretty tempted to load 7 on it but i just didnt see the point, it was working and coping and i had no need for 7.
Next is my laptop, about 6 months old and is running windows 7 (lovely). My main one used is the laptop although at the moment I am using the desktop because the charger has broken on my HP laptop
and ebay sellers arent the kindest people (long story).
Now what I have done is left both and instead concentrated on the programs and documents on each. With the thought being on being able to use any computer at any time if anything was to occur (such as a broken charger). So let me just say I did/do the following:
Syncplicity: I use this file backup thing and just simply tell it which folders to backup. So it uploads them on the web using my email and a password which means I can access my documents online and on the computers I choose. I only need the free one which is 2gb and then any extra by people joining thanks to me etc. Maximum its about 4-5 gb which is ok for me seeing as I dont use much.
Dropbox: The same pretty much which installs a folder on my computer/s and then back anything up inside that folder on the computers i say. So overall my documents are constantly backed up and any computer i choose and i can constantly choose.
Next with the programs I spent a day with both and just loaded the programs I needed on both. Mind you i didnt load all the unneccesary ones on the Xp cause i dont what it to die on me
Now that was just as a background for your personal situation, I advise:
HP DV4000- Well quite rightly i would wipe it and load AV like AVG which i love. I would leave it would Xp...
Toshiba Sattelite- I would leave this also with Xp because is it worth the move and its likely to cause maybe issues. I personally though and your opinion might change. Although having said that it would be nice with 7 but again is it worth it?
HP desktop- Now heres a chance to probably go to windows 7. I dont like vista at all
and the desktop being a strong (?) most powerful machine means it would be nice to have a windows 7 in the house. Its most likely to cope and hopefully all will be well.
Now hopefully you agree but this is my opinion. XP AND WINDOWS 7 are good OS's so even what youve got is good (i just dont like vista). This combined with the software i mentioned is a good idea and will hopefully provide a good experience. P.S. Look at the website of dropbox and syncplicity which both have free options and cost ones for different sizes, have a quick look and they are easy and reliable and also will mean you can easily move around.
I use both but if you want either then give me a shout and ill post the links to make an account and give me an extra 0.25gb