i have Win xp installed: how to install ubuntu 10.04 in dual boot mode?

Resize the WIndows7 partition while booted to Windows7, be sure your data is backed up in case of catastrophe. You can then install Ubuntu to the free space.

Be sure you MD5 test the ISO you download and if you use a CD then burn as SLOWLY as possible.

@ actionparsnip (andrew-woodhead666)

Sir I am a regular user of this site, I read almost all the questions here. Can you explain Why the slow burn is necessary ? Is this true for all purpose ? Actually I have faced lot of burning problems. Lots of DVD has damaged due to wrong burn.
thanks

Slow burning make a darker image on the CD surface, BIOS booting CDs can prefer this as their OS is basic. The slow burn also makes the effects of errors (as CDs use moving parts), affect less of the disk space. The darker image on the CD also degrades slower over time (CDs do degrade as they are optical, think of a poster in the sun and the colours look faded).

All in all a slow burn is great for bootable CDs, burning fast probably saves you about 30 to 60 seconds of real time which is nothing.
I alsoadvise you set the burn going then don't use the OS til it is done, this can help too. If you want an easier life (and faster) use an SD card or USB storage to install with as there is no movable components.