Well, honestly, yes, you can mod it. Just like you can mod anything. It's just up to you, how much or how little you want to do with it.
haha thats the same as my family uses (i won't let them near my computers)... compaq presario 7000 something right? of course it's moddable. my bed is moddable (although my parents wouldn't appreciate it) I know they have bad cooling (i even added a fan!). maybe do something with that. the classic side window would work although going by its location a top window looks like it would be better. perhaps sand down the front plastic bezel thingy to give it a frosted look and put some LEDs behind it (and remove the compaq logo!!). I'd do the same to ours but my mom probably wouldn't like it and the hardware is getting pretty freakin outdated (still perfectly usable, although a defrag would sure help as would cleaning off my 5 year old crap on it... 800mhz slotloading athlon... dunno what else but it was good when we bought it)
Those little Compaq cases are built very well, but you have to realize that that case is totally proprietary and if you sink a lot of time & money in the case mods... almost nothing will be upgradeable as a standard ATX board will not fit that small case. Just something to think about.
Side window spray the metal black or dark metalic blue dye the plastic black or dark metalic blue uv inside's with UV cold cathode