As above, deleting it is going to make no difference to speed at all, but also should do no harm.
Window7 in general need higher spec hardware to run than windowsXP did, one of the main things it requires is RAM. with XP I'd suggest 1GB as being a reasonable minimum, with windows7 I'd suggest 2GB as being a reasonable minimum amount of RAM, so if your computer has less than 2GB of RAM consider upgrading it. (check RAM by right clicking on computer and selecting properties)
You can also make windows7 a lot faster on machines that are at the lower end if it's system requirements by switching off all the "fancy effects" by right clicking on computer on the start menu, select properties, then click on the "advanced system settings" on the left pane then click on settings under the performance heading and make sure adjust for best performance is selected.