Firstly, I wouldn't bother trying to put windows 7 on an inspiron 1520 unless you upgrade the chip to a fast dual-core & upgrade the ram to 2gb or more.

You can download an Win 7 installation disc (from the usual 'dodgy' sources - I won't post the names of these places on a public forum) and burn it to cd using another pc.

But again, personally, if its a standard inspiron 1520 - leave it running on WinXP. Will work much faster. Again, WinXP installation cd's can be acquired from the usual places.

In your current dilemma - you need a windows disc to make it run again - whether it be windows 7, or XP.

If you're lucky, you may be able to go into the BIOS and check for a secondary partition on the HDD for a recovery partition & recovery options.